Super tricky Cory substrate Q

[kletian]

Hi everyone,

I have been corresponding with the fine folks down at WWM about my cory problem, and they suggested that I try here (heard there are some real cory experts). I will post the correspondence below, and please comment if you have any idea what to do! Thanks!


Cory/Substrate Problem

Postby kletian on Tue Oct 21, 2008 5:26 pm
Hi everyone,

I have a rather complex problem that I've run into. This is a sort of carry-over from my other topic, but it's a different topic so I am making a new thread.

Way back when I first started my 36G, I put in Eco-Complete substrate and 6 cories. The aquarium was moderately planted. Well, for a few months, all was well and the corys were growing bigger and their whiskers were nice. Then, after a few more months, the cories started dying off. I could see that their fins and barbels were deteriorating. Naturally I thought it was because of nitrates, so I took a nitrate test from the bottom of the tank, and it was <10 PPM, the same as elsewhere in the tank. I was sort of perplexed, and I had a couple of cories in my 10G quarantine. I moved the cories over and within a week 1 of them died and the other showed huge fin and barbel decay. So I moved all the remaining cories over to the 10 G, about 5 of them. The 10G tank had just normal blue and white gravel from the pet store, nothing special. For a few months, their fins started growing back... but the barbels never grew back. In fact, the barbels kept getting shorter and shorter, and they all eventually died.

I am wondering what's wrong with my aquarium? I don't think it is dissolved waste, because they have always tested <10 PPM, and of course 0 Ammonia and nitrites (weekly water changes of ~30%). I had been keeping platies and angelfish in the 36G and a beta in the 10G, and no one ever got sick or experienced fin rot... except for the cories. I am wondering what went wrong? Was something wrong with the substrate (aka should I used rounder or smaller gravel?). I am at a loss! I don't want to give up on cories because I love them, but I don't know what else to do! Do you think the dying plant leaves in the 36G contributed to their deaths?

Re: Cory/Substrate Problem

Postby Heidi on Tue Oct 21, 2008 6:24 pm
Just some thoughts... What is your ph and hardness? Have you added salt to the tank? I haven't used eco-complete, so can't comment on that. Cories are sensitive to sharp substrate, that we know. What are you feeding? Sinking food? Have you tried a different test kit for nitrates? Are you using the liquid tests or test strips? Do you vacuum the gravel every time you do a water change? Another thought could be waste built up under decorations in the tank, or even under plants like java moss. Since cories are bottom dwellers (with the occasional sprint to the top!), they are exposed to whatever there is on the floor of the tank. Did you buy all of the cories from the same place? Sorry, I'm just throwing ideas out there - I hope you find the cause of the problem soon! Hang in there!
Heidi (aka "MyTai")

Re: Cory/Substrate Problem

Postby platytudes on Wed Oct 22, 2008 6:14 am
What I would do, is take a scoop of your substrate, put it in a glass, pour distilled water in (distilled is best, don't use tap or spring water) and stir it up, then let it settle. It might take a while for the water to settle. When it does, test a sample of the distilled water by itself, then test the water in the glass with the Eco-Complete. Compare both readings. The reason I say this is, when I read your post, a little light bulb turned on and I remembered reading about "bad batches"...
http://www.google.com/search?hl=en&q=ba ... gle+Search

See if the tests tell you anything, for example if the substrate alters the pH, hardness, alkalinity, etc. If it doesn't elucidate anything, then next step, I would be calling/e-mailing a CaribSea representative.

The fact that platys didn't get sick in your tank seems to show that you didn't have a problem with pH, alkalinity and hardness dipping down too low (do post those results Heidi mentioned, it would be interesting - another clue!) even though the symptoms you mention really do sound like acidosis. The same sorts of symptoms happen to hard water fish kept in soft water. Do let us know if you used salts or pH altering chemicals...I'm with Heidi's train of thought, this sounds like a water chemistry issue, not a water quality issue.

Keep us posted!
Nicole
Give a man a fish, and he'll eat for a day. Give a fish a man, and he'll eat for weeks!

Re: Cory/Substrate Problem

Postby kletian on Wed Oct 22, 2008 7:55 am
Thanks for all the helpful suggestions so far! To answer the questions...

The pH is around 8. I don't know the hardness, but I think our water is quite hard (Southern California). I am feeding the cories sinking shrimp pellets, and whatever else manages to fall to the bottom of the aquarium. I used two different liquid kits for nitrates, and both came out very low (10-20, and < 10). I use a 30-60 gallon tank filter on a 36 gallon tank, and my aquarium is not heavily stocked along with weekly water changes. Every time there is a water change, most of the water comes from the bottom of the tank, as I thoroughly vacuum the gravel with a siphon. Ever since I thought it could be buildup under the java moss, I have gotten rid of all of it, and there is only one piece of driftwood in the tank which is siphoned under. I bought some cories at Petsmart and some at Petco, and regardless of where I bought them, the ones I bought first thrived for a few months before dying, and the ones I bought after just started dying when I put them in the big tank. The big confusing question comes when I look at the effects of moving them into the 10G quarantine; fins grew back but whiskers did not... it seems to slow the rate of death, and the only major difference between the two tanks is that one uses normal gravel and has no plants, and the other had EC with plants. Further, putting them in the 10G quarantine did not allow them to thrive, because they all succumbed before their natural lifespan (maybe last a year or just over a year), so I realize the 10G didn't provide a solid solution either.

I would test the EC, but the cories still died in the 10G tank without EC, so I am not really sure what is wrong... unless there is a problem of substrate in BOTH tanks. The 10G quarantine uses your run of the mill gravel (blue and white) which is not especially smooth (slightly jagged). Of course I would never use salt or pH altering chemicals; those are bad! I only dechlorinate.

Please let me know if you have further thoughts! I love cories but I won't buy any more if I can't keep them alive

Re: Cory/Substrate Problem

Postby platytudes on Wed Oct 22, 2008 8:33 am
This turns out to be a real stumper. I would try writing the WWM crew in addition to posting here, and posting on a few different forums, such as planetcatfish.com (where I have read people have gotten responses from reknown cory expert, Ian Fuller) and fishforums.net (where I know Inchworm and Coryologist are two cory experts, and Ian Fuller who goes by the name Coryman there, posts occasionally)...The more people evaluating your situation the better, because your question doesn't have an obvious answer. I'm glad you don't add salt or pH altering chemicals, but you wouldn't believe how many people do, because they have been told that plants can't grow in high pH, or platys like salt...all distortions of the truth. That's why I had to ask, just to make sure!

It sounds to me like the reason the barbels didn't grow back is because whatever wore them away, did so beyond the soft tissue. Same thing happens with finrot, if the damage extends beyond the soft tissue, the tail will not grow back properly or at all. (That's my very unscientific explanation ) Don't get too hung up on the fact that fins grew back and barbels didn't, while it is a point worth mentioning should you consult others, it is probably not indicative of a substrate problem in both tanks...just the extent of the damage to the barbels vs. fins.

You still didn't mention what species of corydoras this was, do mention that when/if you post in other places. Not to sound negative, but I don't know that anyone in this forum is particularly a cory expert, so may have to broaden your horizons...
Give a man a fish, and he'll eat for a day. Give a fish a man, and he'll eat for weeks!

Re: Cory/Substrate Problem

Postby sump'nfishy on Wed Oct 22, 2008 8:47 am
perhaps there was a fish picking on them that you didn't see, or they were squabbling at night?
-Danyal

Re: Cory/Substrate Problem

Thanks for the suggestion. I'll hop on over to planetcatfish and repost my question along with some of your answers. I have emailed WWM and Neal tried to help... except that his suggestions included removing the Java moss and vacuuming the gravel thoroughly, which I do already. As for the wearing of the barbels, some of them I moved to the 10G while only half deteriorated, and they deteriorated the rest of the way (albeit at a much slower rate).

The species of cory are your typical Bronze (Aeneus) Cory, Leopard Cory, and Julii Cory, which are all available from Petco/Petsmart.

This is just not possible in the 10G, as there were only 5 cories and one betta fish.

[nikelodeon79]

First off, I am NO expert, but I have experienced a similar problem in the past.

Was something wrong with the substrate (aka should I used rounder or smaller gravel?).

I would actually not recommend gravel at all. I only use very smooth, small grained sand for my cories. The grains should all be of a uniform shape and not vary too much in size.

Food tends to get trapped between the cracks in gravel. Can you picture the little cory with his delicate barbels trying to move it aside to get to that food? And then the longer the food sits there, the more rotten it gets... can lead to dangerous gasses. No matter how smooth the gravel is, it can be an issue.

I've also had issues with sand. I used Tahitian Moon Black Sand in one of my cory tanks, and the results were pretty disasterous. I had cories dieing of barbel erosion/infection right and left. I then switched to a silica sand I purchased from a chain hardware store (Menards) and the difference was remarkable. I took a picture of the two sands side by side:


You can see how much more round the lighter color sand is. I could immediately tell the difference when I was washing the new sand. The TMBS had felt somewhat abrasive... not so with the white sand!

There are definitely differing opinions as to whether or not cories need sand. I feel that they do... some others might feel that they don't. Regardless, seeing my cories happily bury their little faces in the soft sand was enough convincing for me!

[andywoolloo]

that's interesting on the tahitian moon sand, my cories were on it, no problems?

i totally agree on sand for cories. Altho nice smooth gravel can be ok too.

[Supercoley1]

Again I am not a Cory expert but I do have some Schultzei in my tank.

I was always under the impression that silica sand was a no no for the freshwater setup as it plays with the hardness. Not sure on this, maybe something I read that was wrong info.

On the subject of Nitrates I don't know why you are worrying or even being told to worry about them. 10-20ppm nitrate is not a lot in a planted aquarium. Many people in the planted side of the hobby including myself add nitrate in the form of Potassium Nitrate on top of the natural nitrate caused by decaying organic material and filter bacteria production. I personally add 3ppm a day, no idea what my total is because I don't test for anything. People using the EI method are aiming for 20-30ppm as their standard.

I know many people with EI setups that have kept corys for many years with no problems at all. I had 1 cory die last week from what I am told maybe a bacterial infection but the rest are OK so I can only assume it was an isolated case for this one fish. I only do 10% water changes a week and I don't clean the substrate (which is playsand on top of Tropica Organic clay on top of Leonardite on top of mulm) yet I have no problems with any fish other than the above mentioned. I would therefore allay your fears over the cleaning and nitrates causing problems (within reason of course.)

This is Eco-Completes answer to the Ph and Kh question:

'While Eco-Complete™ Planted does not affect pH and KH long term, you will find that it will give a small bump to both of these parameters initially, and this is especially noticeable with the use of RO /DI water. Fortunately this is just a small amount of Calcium Carbonate that is on, not in the substrate and it will dissipate with the first couple of water changes, usually in the first couple weeks. Planting the tank will also help. Keep in mind that one should never add particularly sensitive animals to a tank in the first few weeks anyway but that this is especially important with this situation if the animals are pH sensitive- requiring a low pH.'

There are 3 types of Eco complete which are 'planted', 'planted red' and 'Floramax'
The advice CarbiSea give is that the first 2 are unsuitable for soft bellied fish, which I assume the corys are but are suitable for burrowing fish. The last one is suitable for soft bellied fish but not burrowers. I would assume that to keep corys you would need a substrate which was suitable for soft bellied and burrowers which would rule out all 3 versions.

However saying this most people on lots of forums that have EcoComplete and Corys say it is fine and no problems. It may be CaribSea playing safe. (The first 2 are rounded and should be OK whereas the Floramax is definately unsuitable as it is sharp and larger.)

So maybe not much help but I would look at the possibilty of disease in the tank or maybe the substrate is doing something strange!!!

AC

[nikelodeon79]

I was always under the impression that silica sand was a no no for the freshwater setup as it plays with the hardness.

I believe almost all sand is silica... other sand just isn't specificially called "silica sand." (Playsand, beach sand, etc.)

I did a test on my sand by leaving it in a glass container with tap water for a couple weeks. I tested the water at the beginning and the end and there was no change in pH, GH or KH.

[MatsP]

Silica sand will not affect hardness (or in any other way change the water chemistry), and as stated, play sand and many other "plain forms of sand" are indeed silica sand. Silica sand is what is used to make glass. It is not quite the same as "ground glass", but it's not that far off either.

What you do not want is coral sand - that will affect the hardness.

I have play-sand in several of my tanks.

--
Mats

[Bas Pels]

Sand is silicium oxid (formally silicium dioxid, SiO2)

However, in the sand we see, normally a bit of somthing else is mexed in - therefore red sand, yellow sand en white sand can excist. Siliciumoxid does not dissolve, and will thus not influence the water parameters. However, the other components may be able to dissolve, and have an influence.

[apistomaster]

I think all of the substrates you used are fine for Corydoras although the sands that allow them to dig deeply in and sift out through their gills is closer to the types of sand wild Corydoras prefer.

I think your problems have much more to do with the initial condition your Corydoras were in when you bought. Next problem is your quarantine procedure.
Most bacterial diseases are secondary to a primary disease, parasite or some profoundly stressful period they have been through before you ever bought the fish. I have a few recommendations regarding your quarantine techniques. They are based on my own methods and are by no means the only way to handle QT Corydoras or any other fish.
1.I would supply the quarantine tank with a thin layer of fine silica sand no more than 1/4 inch thick.
2. Ensure the quarantine tank is set up with a sponge filter that you have run in an established tank for 3 weeks.
3. I would treat the qt tank water with Hikari PraziPro in accordance with the directions of on the bottle.
4. Feed them mostly live foods; live black worms and newly hatched brine shrimp. Then begin to acclimate them to a sinking pellet food.
5. Once they accept the pellet foods well, begin feeding them some pelleted food you have set aside and treat this food with Gel-tek Ultra Cure PX.
I use a small 1 inch diameter prescription bottle. I add a little UC-PX then a layer of food and repeat this until the bottle is almost full. Add just enough water to soften the pelleted food. The food will absorb the medication with the water. Keep the unused portion of the medicated food refrigerated. Feed the fish the treated food 2 times a day and continue to feed a live food once a day. Keep the fish in quarantine for at least 3 weeks and continue to keep the water medicated as I have described. I would also treat them with a malachite green Ich medication once a day for the first week. Change 50% of the water every other day and replace the water and add more PraziPro to make up for that which you removed. Be certain that you siphon any uneaten food that remains after one hour. Live worms may be left. The Corydoras will find them.
The purpose of the PraziPro in the water and UltraCurePX in the food is to reduce the load of gill flukes and internal parasites that can cause the fish to eat poorly and become weak enough for the ubiquitous bacteria from gaining a foot hold. Nearly all Corydoras, certainly those from big chain pet stores are in a run down state with severely weakened immune systems.
Provide the quarantine tank with some caves or small plastic or new clay flower pots and some floating artificial plants. Corydoras need hiding places and floating cover provides further cover which helps reduce the fear Corydoras experience whenever they are out in the open. Everything I'm recommending has as it's purpose, the reduction or elimination of common parasites, prevention of an early outbreak of Ich,
providing an environment that minimizes the stresses induces from lack of secure hiding places. The live foods are usually accepted by even very weak fish and getting some good food in them is a necessary part of improving their natural immune system. The stronger the fish are, the more resistant they become to infections. Your fish die when they have been finally overwhelmed by the various parasites then scondary bacterial infections. I left out the use of an antibiotic because they are rarely needed if you deparasitize your fish and get them eating live foods right away.
My way is not the only way to handle newly purchased fish that have already proven problematic for you but I presented a method that addresses most of the ultimate causes of your latent Corydoras deaths. Others may do things a little differently. There are many ways to do this but if you don't do anything more than begin with a fully cycled sponge filter, a sandy bottom with caves and feed some live foods, your Corydoras survival rate will be better.
Your sand has little if anything to do with why your Corydoras losses have been high.

[Coryman]

Suitable Cory substrate!

Over the years I have used many different substrates for Corys and by far the most suitable is fine smooth grained sand. Smooth grained, that is to say when viewed through a magnifying glass looks like tiny pebbles. This is what most Cory species are living over in their natural habitat and is perfect for their feeding habit, which in the main is that of a filter feeder. They actually take up mouth fulls of sand and filter out any food particles they find and eject the sand through the base of their gills. The food itself can be all manner of things from microscopic organisms, small crustaceans, worms, and insect larvae.

The problem we have in our aquariums when we use larger particle substrate is that food penetrates deep into the substrate and the Corys then have to actually move it around with their barbels, this is unnatural for them and can cause unnecessary ware and irritation to these delicate organs, which in turn can and does cause inflammation and then infection and we have all seen the resulting shortening and even total loss of barbels.

There is also secondary problems with using larger un-siftable substrate is that unreachable food will breakdown and rot causing pockets of anaerobic gasses to build up, which are highly poisonous to any fish that happens to ingest it. Many people will undoubtedly state that they have no problems using larger particle substrates for their Corys, which may very well be true and in the past I have done so myself, however it is not natural for them and it is easy to see what they prefer when you watch them sifting through fins sand.

The pH at 8.0 is also a little high and unnatural for Corys, they are found in waters as low as pH4 in some areas. If possible I would aim for a pH of around 7 to 7.4.

Ian

[StevieD]

A friend of mine has a show tank with Eco-Complete in it and all his Green Emeralds have ended up with Barbel loss. They seem to do fine on Algae wafers, but the barbels have never grown back. He currently has a dozen Discus and other species of the more temperamental fish in that tank, his only issue has been with the barbel loss.

It could possibly be they just do not do well on Eco Complete.

Wish I could offer more info.

Steve

[OldMan]

Two clarifications needed.
Silica sand is one of the many types of sand that exist. Sand is not SiO2, it is a generic name for small rock particles that are too large to call silt or other names that apply to fine particles like clay. Silica sand in general is a very stable sand from a chemical point of view in a typical aquarium setting so it is good in that respect. Some sand is manufactured by crushing larger particles of sand or gravel and the resulting sand has sharp corners on the particles no matter how small they are. That sand would not be suitable for any bottom dwellers.
As far as StevieD's post, I don't doubt that the eco-complete may have been present when his fish had barbel loss but the diet of algae wafers is not a good idea for most cories. Cories are omnivores that will end up with inadequate nutrition on an algae only type diet. Cories need a well balanced diet that is not provided by algae alone.

[MatsP]

Depends on the brand of algae wafers, I expect. In my case, they are the Hikari brand, and they contain just about everything besides algae. Fish-meal is the first listed ingredient, followed by alfalfa meal, wheat flour, wheat germ meal, starch and dried seaweeds meal. Spirulina is indeed one of the ingredients, but there are ten other ingredients listed before the Spirulina. The next three ingredients are "enzyme, asthaxanthin and garlic". I also have a bag of Hikari "Sinking wafers", which has a cory on the front of the pack. The main ingredients are fish-meal, wheat germ meal, wheat flour, starch, soybean meal, fish oil, seaweed meal, krill meal, brewers yeast, enzyme, spirulina.

So whilst I'm sure there is a difference, I'm far from convinced that there is a huge difference in them. Other algae wafers may be different.



--
Mats

[apistomaster]

That black "Moon Sand' is definitely a poor substrate for Corydoras. It is a man made material, slag glass from some smelting processes resulting in a material similar to obsidian and it is fractured producing sharp edges instead of naturally weathered glacial or alluvial deposited Silica sand which has been subjected to erosion forces that tend to round the edges enough to be Corydoras safe or for any other fish that makes sand an integral part of it's life style. My wild discus love to sift and blow the fine river sand I use in their tank. It is primarily silica based. Apistogramma are another group that habitually sifts fine sand for food and needs the rounded particles.
The EcoComplete is marginally acceptable for Corydoras. It is mostly rounded particles and is graded to have a balance of 2mm to ~0.5 cm grain sizes. Many Corydoras do fine with it but some may not. if you feed a low of live worms you are definitely better off if you use fine natural sand because Corydoras urge to dig out live worms can lead to babel damage and subsequent secondary bacterial infection of the wounded barbels. Fine sand does require attention to the prevention of anaerobic decay and using it in thin layers of 1/4 to 1 inch thick is safer than sand beds any deeper.

FloraBase is rather expensive specialized plant substrate that is a good material for Corydoras. It is a bit too coarse sizes to permit them to sift it through their gills but it does have rounded edged particles of a relatively soft material which is easily moved by the Corydoras sticking their snouts in it. I use less than 1/4 in of Florabase in most of my breeding and rearing tanks including those in which I keep and breed my various Corydoras spp and it has never caused any problems of barbel erosion or infection. Here is an example:


Much is made about the value of Spirulina fish foods for algae eaters but fish do not really care much for the actual Spirulina regardless of how good it may be for them and it must be disguised adequately with foods fish actually like.
I use the pure Spirulina powder in my beef heart blend but I learned long ago that a little dab will do you. I add no more than 1/2 tsp Spirulina powder/cup of cleaned raw beef heart. I find that the dried seaweed is more readily accepted and I'll include a couple sheets of it along with that 1/2 tsp of Spirulina powder/cup raw cleaned heart. While I make the beef heart mix mainly for raising Discus it is a food that even my Corydoras eat well. The secret is cleaning the indigestible connective tissues, blodd vessels and all fat from the pure muscle. The processing is as important. I run mine through a fine meat grinder then blend it to a fine puree in a blender and rely on agar a the binder for the resulting fine particles which even small fish can eat. Minimizing the binder, be it agar or unflavored geletine is necessary. the addition of freeze dried blood worms adds nutritive value but as importantly, the worms are folded into the pre-blended pureed ingredients to act as fiber reinforcement that enhances the cohesion of the chunks of heart. many unsuccessful beef heart blends fail because too much binder is used resulting in a food with the consistency of rubber. Only large predatory fish can handle such botched batches.

[DarrellAR]

The previous posters all make sense; here is another consideration. Many agree that when raising cory fry you cannot let bacteria build up on the glass bottom becuase the bacterial load is more than they can handle. It must be wiped clean about every 3 days. Bacteria or bacterial slime builds up in any tank on all the surfaces not just the surfaces of the biological filter which in many cases is the sponge filter. Bacteria will build up on top of the gravel in the same way. You can easily feel the bact. slime on the inside of the glass and even on the gravel. The longer the tank is set up the heavier the coating is. Tanks set up for a year with heavy feeding would have heavy bacterial coatings. As in the baby cories this has to add to the load on the corys immune system. Combine this with wear from sharp edges and an improper ph or other stess inducing anomalies and the fish could be overwhelmed; starting with their barbels and proceeding. Stress causes organisms immune systems to not function well. Smooth edged sand would have another benefit: it is plowed by the cories. That is, the surface that would have the most bacteria gets turned over leaving sand from under the surface on top; that having less bacteria giving the fish's immune system a rest. Having bacteria albeit not vurilent bacteria constantly introduced into small cuts and abrasions on their barbels is not a good thing. Taking off the top layer of a tanks gravel bed and disinfecting it can't hurt provided the tank has sufficient beneficial bacteria to handle the load. In the wild corys would always be on surfaces with low bacteria counts. Having a biological filter not in the tank like a back filter or other external filter with heavy bacteria colonies and moving the water over these beds quickly will help remove the food for the bacteria from the water column and minimize the bacteria build up in the tank. Darrell

[Coryman]

It looks like the topic have divided into two. Substrate & Food.

The danger with large particle substrate is the fact that food particles will penetrate out of reach of Corys and without regular substrate cleaning will rot down and foul up and may even create anaerobic gas pockets, which are highly poisonous. Sometimes it is extremely difficult to find out what the natural substrate is for a particular species. In a lot of cases the natural substrate is covered by rotting leaf litter or just plain mud and it may even be several feet deep. The use of large particle substrate in my opinion is not ideal and yes, I know many people do use larger size substrate and do not have any problems with it.

On the food topic, again there will always be debate, but one thing that keeps coming up is the use of algae wafers and algae pellets. Some algae may form part of the dietary requirement of Corys, but generally they are considered as omnivores and filter feeders, sifting out food particles from the substrate and bio-film. Again only my opinion, but pure algae based foods are not going to give Corys their necessary requirements. Another thing I feel needs a mention is that some food manufacturers use MSG (Mono Sodium Glutamate) in their foods, this in mine and many other peoples opinions is not good, this substance is a flavor enhancer and because of this has an addictive effect, encouraging those that eat the product that it is in to want more. It has no benefit to a fishes or human diet whatsoever, in fact it's only benefit from it is to the manufacturer. I believe many food industry watchdogs are trying to ban it's use in human food products.

Ian

[MatsP]

Another thing I feel needs a mention is that some food manufacturers use MSG (Mono Sodium Glutamate) in their foods, this in mine and many other peoples opinions is not good, this substance is a flavor enhancer and because of this has an addictive effect, encouraging those that eat the product that it is in to want more. It has no benefit to a fishes or human diet whatsoever, in fact it's only benefit from it is to the manufacturer. I believe many food industry watchdogs are trying to ban it's use in human food products.

I agree that MSG is not of any benefit to fish or humans - it is added as a "flavour enhancer" in human food [it doesn't add flavour as such, it appears to increase the flavour already in the food], and I expect the reason for it being added to the fish-food is the same "make it taste more" without actually having more tasty ingredients. It may also make the food "smell more" in the water, which makes the fish find it better - but again, this could be solved by adding more flavour.

I also agree that algae wafers isn't what you SHOULD feed Corys - although depending on the brand, it may not be a BAD substitute, it's still not the food intended for this type of fish - I feed my corys a mixture of frozen foods, Tetra Bits/Prima and Tetra Tabimin - all of which seems to be happily taken.

--
Mats

[Bas Pels]

Just to explain how MSG can enhance flavour without having any:

The taste organs in one's tongue will have to inform the nerves about the information, andthis is done by chemicals. The nerves use these chemicals among themselves too, and quite a few of these have been discovered

One of these is glutamate acid

Therefore MSG mimics the information send by the taste organs to the nerves. It makes the nerves more sensitive to the real message from the senses, so that, if a little is found, the signal will say much is found

It does more, however, I always get a strange feeling in my mouth, and get thirsty from it, the stuff is mostly used in Asian cooking, which I happen to like