Chronic Cory fin rot problems

[Mol_PMB]

I've had a tank set up for more than 18 months with a small group of Cories in. There are presently 5 Corydoras oiapoquensis and 3 Corydoras condiscipulus, and no other fish.
Gradually the fins on all the Cory oiapoquensis have suffered from fin rot and although I have tried a few things I have failed to stop it. I'm now getting concerned about them and would like some advice.
I have attached some photos of the affected fish and a general view of the tank.

Answers to the template questions are appended below.

Any help/advice would be much appreciated - thank you!

Regards,
Paul



1. Water parameters
a) Temperature range - shows as 24.5 on the alcohol thermometer and 25.5 on my conductivity meter. Pretty stable throughout the year.
b) pH - acidic typically 6.0 to 6.6
c) GH - 1 to 3 dGH
d) KH - 0 to 0.6 dGH
e) Conductivity - in the range 200 to 300 uS
f) Ammonia, Nitrate, Nitrite levels - Ammonia and nitrite zero, nitrate up to 40ppm (I use plant fertilisers)
g) Water change frequency - weekly, 30%
h) "Routine" water treatments - Prime dechlorinator in new water, EI plant fertilisers (but at much lower doses than used for 'true' EI fertilisation)

2. Tank set up
a) Size - 30"L x 12"W x 15"D, approx 90L
b) Substrate - mostly silica sand with some rounded pebbles
c) Filtration - HMF with 1400litre/hour pump piped to the opposite end of the tank to create a unidirectional flow along the tank with high oxygenation.
d) Furnishings - rounded stones, bogwood, Echinodorus plants, based on an online video of Cory oiapoquensis in the wild.
e) Other tank mates - none at present. About a year ago I briefly had a group of 8 Hyphessonbrycon takasei in there, which died off one by one over the course of about 6 weeks shortly after I got them
f) How long has it been set-up? - 18 months
g) Food used and frequency - I generally feed daily, a variety of foods including Vitalis catfish pellets, Tetra prima, frozen or live bloodworms (or other frozen foods), 'Golden Pearls', live grindal worms.
h) Recent changes in the tank which occurred shortly before the disease/problem appeared - The problem has gradually become worse over the past year, no sudden changes.

3. Symptoms / Problem description or history - The fins of the Cory oiapoquensis are gradually rotting away and some of them now look really bad. The Cory condiscipulus look OK.

4. Action taken (if any) - medications, see below

5. Medications used (if any) / changes in fish observed since treatment began (if any) - Over the past few months, I have tried treating the tank with Melafix, and at different times with Interpet #8, anti fungus and finrot. These have not solved the problems.

[bekateen]

Hi Paul,

I'm curious - Are you having any fin rot issues with your other corys (melini and burgessi) or your Brochis?

Cheers, Eric

[Mol_PMB]

Hi Eric,

I have cories in three of my 11 freshwater tanks. In addition to the 90L Oiapoque tank, the 450L has a group of 8 Brochis splendens and the 240L has 13 Cory melini, 9 C048 and 7 Cory burgessi.

None of these have any fin rot problems, nor do any of the other fish. Water parameters are similar in all these three tanks (and most of the others too).

I'm hoping a Cory expert can come up with some advice on how best to treat this.

Thanks,
Paul

[bekateen]

Thanks for the info Paul. What about wood or other decorations? Obviously the fin rot is probably disease driven, but it should be curable unless some element in the tank is either harboring the pathogen(s) or stressing the fish chronically.

Just thinking off the top of my head with that - not likely productive but once in a while I'll toss such scat against a wall and it sticks. Vioila, brown paint!

Cheers, Eric

[cowboyish1]

I just posted a similar issue with c. similas. The top fin on the one picture you posted is very similar to what's going on with mine. I'm stumped. I hope we both find answers.

[Mol_PMB]

Eric,
The decor in this tank is the same as in my 240L tank: the sand, rounded stones, pebbles, bogwood and plants are from the same sources in both tanks and cause no problems in the 240L. I use similar plant fertilisation in all tank so I don't think it's that.
The one thing that is 'unique' about this tank is the use of a high-flow pump and pipework to provide a unidirectional flow along the tank. This was intended to replicate the flow in the video of these fish in their natural environment. It also produces very high oxygenation of the water. I would have thought this was a good thing, but perhaps it can be over-done? The fish don't struggle against the current; those with good fins like playing in it. The water flow squirting into the tank is quite noisy too. Could they be stressed out by the noise of rushing water?

Cowboyish, I hope we can get some recommendations.

[Mol_PMB]

One of my reasons for raising this question now is that in 10 days I have the chance to get some more fish appropriate for this tank, with a choice of Cory oiapoquensis, C134 or Cory amapaensis (all native to the Oiapoque). I'd love to increase the shoal size, but I don't want to introduce new fish into a tank with problems that I don't understand.

[Mol_PMB]

Any more thoughts / ideas / suggestions ?
More food? Less food? Cut out the plant ferts? Reduce the water flow or noise?
More fish? Add coral gravel to raise hardness and pH?
Thanks,
Paul

[catfishchaos]

I would cut back on feeding to every other day and increase water changes to 50% every 3-4 days. The amount of waste those cories produce is probably sufficient to cease the addition of fertiliser (definitely after you add more cories)

[Mol_PMB]

Thanks
So you think the high nitrates are the issue?
It's quite possible, maybe this species is particularly sensitive to them.
I'm happy do do more water changes to keep them down, is reducing feeding likely to weaken them stuff further though?
Cheers,
Paul

[catfishchaos]

Thanks
So you think the high nitrates are the issue?
It's quite possible, maybe this species is particularly sensitive to them.
I'm happy do do more water changes to keep them down, is reducing feeding likely to weaken them stuff further though?
Cheers,
Paul

As my understanding goes Less food= less feces= less nitrate build up but I could incredibly wrong. I'm asking a lot of the same questions here as I am in a similar thread started by cowbyish1 so if the answer is yes to either of these questions I think it would be best that you read the post I just made in that thread to limit my redundancy. I jump to conclusions personally so it would be best to get others to chime in on what they think of the things I have suggested or their own suggestions.

I believe thats an airstone pictured but if I'm incorrect- do you have any surface agitation? if not are you seeing a build up of proteins (looks like an oil slick) on the surface?

When you do your water changes do you vacuum the sand?

[Mol_PMB]

Thanks - I'll have a look at the other thread.
There's no airstone but there is very vigorous surface agitation from a high-flow pump and spraybar. It's really noisy, with a flow of 1400 litres per hour in a 90L tank. I set it up this way to mimic the flow in the video of their fish in the natural habitat.
I do vacuum the sand when doing water changes, in practice the fish themselves do a pretty good job of keeping it turned over too, and the high water flow takes any detritus to the filter.

[dw1305]

Hi all,

So you think the high nitrates are the issue?

I think it is unlikely. Often when people have high NO3 values it is the "smoking gun" from previous high levels of ammonia (NH3) and nitrite (NO2). It is different when you add inorganic NO3 (via KNO3 etc.), the NO3- ion itself isn't very toxic.

cut out the plant ferts?

You could certainly try this, I don't know what fertiliser you use, but your Echinodorus has fairly low nutrient demands, and you are right it doesn't need anything like EI levels of fertiliser. If the flow isn't so large that it precludes the use of a floating plant? you could try just adding fertilisers via the "Duckweed Index" (http://www.planetcatfish.com/forum/view ... hp?t=36231).

Add coral gravel to raise hardness and pH?

I don't know what the water conditions are like in their native habitat, if the water is harder there that might be an option (you can use "oyster shell chick grit", rather than coral gravel). I'll assume the water is very soft naturally, so I don't think that is the problem. I'm adding leaf litter to all my tanks now (all rain-water) and I think it definitely helps with fish health.

.......and the high water flow takes any detritus to the filter.

You have high flow, which makes low levels of dissolved oxygen unlikely, but I would definitely put a pre-filter on the filter intake. I like the large foam blocks they sell for Koi ponds etc. (http://www.planetcatfish.com/forum/view ... hp?t=31213), I've always used a foam pre-filter, but over time I've used larger and larger ones. The Eheim prefilter (https://www.eheim.com/en_GB/products/ac ... _prefilter) is also an option.

If detritus is slowing the flow of water through the filter media your microbial biological filtration may be running at a fraction of its potential, and you may have continually elevated levels of NH4+ and NO2-, which are definite possibilities for your fin erosion. I don't have any floss, or fine foam, in a canister filter, I have all my mechanical filtration by the pre-filter, and I used floating cell media, Eheim coco-pops, Siporax, alfagrog etc in the filter body.

It is possible to have simultaneous nitrification and denitrification in a canister filter, but if you have plants you don't need to deplete the NO3 by denitrification.

cheers Darrel

[cowboyish1]

If water parameter testing is done weekly, and the tests always show 0 ammonia, 0 nitrites, and low nitrates (5-10ppm), could it still be a microbial biological filtration issue?

[dw1305]

Hi all,

If water parameter testing is done weekly, and the tests always show 0 ammonia, 0 nitrites, and low nitrates (5-10ppm), could it still be a microbial biological filtration issue?

It can be. There are plants, and "plant / microbe" systems are much more efficient than "microbe only" systems, but you could still have a constant trickle of ammonium and NO2 from the filter, and plants don't tend to directly take up nitrite.

There is some very interesting work being carried out at the Humboldt-Universität zu Berlin, Department of Biology in Freshwater and Stress Ecology, where they are looking at the importance of humic substances in fresh-water (thanks to Marcel of UKAPS for this link <http://ukaps.org/forum/threads/stress-ecology.43106/>).

5. From Brazil come even more exciting reports: In very soft, humic freshwaters, such as the Rio Negro, humic substances stimulate the uptake of essential ions, such as sodium and calcium, even at extremely low pH (3.5-4.0) and prevent the loss of ions induced by acid waters. Consequently, humic substances are the very biogeochemical basis, which enable fish to survive in these extreme environments. http://www2.hu-berlin.de/biologie/aquao ... o=research

There is more here from Dr Christian Steinberg (in German) about the importance of humic substances in freshwater ecosystems: <http://files.feedplace.de/haustier-radi ... stoffe.MP3>

The problem with relying on the results from water testing, is that there are a lot of variables that can effect the results you get, particularly for nitrate (you can't directly use colorimetric techniques for nitrates, because all nitrate containing compounds are water soluble). It isn't that you can't get accurate results, you can, but for nitrate and ammonia (as ammonium) an ion selective electrode (http://www.coleparmer.co.uk/TechLibraryArticle/971) is probably the best option. Nitrite is easier to test for, but you are still interested in very low level determination.

cheers Darrel

[Mol_PMB]

Hi Darrel and many thanks for your ideas - sorry for the delay in getting back to you but I've been away from home.

Since completing the fishless cycle on the tank about 18 months ago, I've never seen ammonia or nitrites when testing but I suppose there could be transients after feeding. The tank's not heavily stocked and has plenty of filtration so I wouldn't expect this to be a problem. With the water being acidic, ammonia is less of a risk anyway as far as I understand.

The flow is far too high for floating plants. I do use a variety of floating plants on some of my other tanks but unless I reduce the flow on this one they'll just get blasted.

I don't know exactly what the water hardness is like in the Rio Oyapock / Oiapoque. I imagine that it's soft and acidic like most South American rivers (and like the water in my tank) but perhaps I'm wrong. A quick google finds several indirect mentions of it being soft, acidic and warm.

My filter is a Hamburg Matten Filter, curved in one corner of the tank and approximately 15" x 18" x 2" thick. In the space behind is the heater, electric pump and a load of alfagrog. The 1400 litres per hour has to flow through the sponge, and I siphon the face of the sponge from time to time. There is typically a small difference in water level across the sponge but less than an inch.

I've just tested the water for toxins, about 90 minutes after feeding. Ammonia and nitrite are a clear zero, pH is 6.6, conductivity 310uS.


I'll increase the frequency of water changes and reduce the plant fertliser and see what happens. I'm also tempted to enlarge the holes in the filter spraybar to reduce the noise and flow velocity a bit.

Best Regards,
Paul

[dw1305]

Hi all, hi Paul

....I don't know exactly what the water hardness is like in the Rio Oyapock / Oiapoque. I imagine that it's soft and acidic like most South American rivers (and like the water in my tank) but perhaps I'm wrong. A quick google finds several indirect mentions of it being soft, acidic and warm.

OK, "soft, acidic and warm" would have been my guess.

My filter is a Hamburg Matten Filter, curved in one corner of the tank and approximately 15" x 18" x 2" thick. In the space behind is the heater, electric pump and a load of alfagrog. The 1400 litres per hour has to flow through the sponge, and I siphon the face of the sponge from time to time. There is typically a small difference in water level across the sponge but less than an inch.

Even better, I think that probably allows you discount water quality and dissolved oxygen as an issue. HMF's typically provide very good quality water.

I've just tested the water for toxins, about 90 minutes after feeding. Ammonia and nitrite are a clear zero, pH is 6.6, conductivity 310uS.

The conductivity is much higher than I would have expected, do you know what your tap water is?

The only real suggestion I have is to add some tannins, Oak (Quercus spp.) leaves and Alder (Alnus glutinosa) "cones" (http://www.planetcatfish.com/forum/view ... hp?t=19561), would be PYO options.

Terminalia catappa (IAL) would be another option, and some people are having great success with Rooibos tea (http://www.planetcatfish.com/forum/view ... hp?t=40948)

cheers Darrel

[Mol_PMB]

Thanks again Darrel.

Tapwater conductivity is 130uS/cm.

I've just done a 30% water change on the tank without any fertilisers, and then added a new dose of Interpet #8.
Conductivity in the tank is now 240uS/cm.

I've removed the filter spraybar and replaced it with a plain piece of pipe. The water flow is still the same but the velocity is much less, so it's quieter. The water surface is still rippling. I have added some Limnobium laevigatum and some Hydrocotyle leucocephala as floaters.

I'll do another 30% water change on Wednesday.

I'm going to trade in some of my Farlowella and L397 juveniles on Saturday, and hopefully get some more Corydoras to replace them. They can go in a QT for the short term but my medium-term aim is to put them in this tank.

[dw1305]

Hi all,
Best of luck. Can you get some Alder cones?

cheers Darrel

[Mol_PMB]

Ah, sorry, I forgot to mention the leaves etc.
I do regularly put oak, beech or catappa leaves in the tank, and there are some in there at the moment. I ran out last week and collected some more yesterday. I haven't found a nearby source of alder cones but I'll have a look this weekend.
Many thanks,
Paul

[Mol_PMB]

These are the two videos I used to set up the tank decor, and as you can see they both feature rapid flow, sand, wood and leaf litter. There's also a sequence with small pebbles and a wavy-leaved plant similar to the Echinodorus I selected:

https://www.youtube.com/watch?v=yGx__0JDZls (from about 2:45 onwards)
https://www.youtube.com/watch?v=cLwvUXC3dHY

[dw1305]

Hi all,

These are the two videos I used to set up the tank decor, and as you can see they both feature rapid flow, sand, wood and leaf litter. There's also a sequence with small pebbles and a wavy-leaved plant similar to the Echinodorus I selected:

Thank you for the video links, I enjoyed them, and your tank look very similar to the rivers.

I have no other suggestions to make, other than the Alder cones, hopefully things will sort themselves out.

Alnus glutinosa is common by streams and lakes etc. and you sometimes see Alnus cordata used as a street tree in supermarket car parks etc. It stays green very late in the year and has much bigger "cones".

I've always collected my own Alnus cones (from all, or any, of A. glutinosa, A. incana and A. cordata), but I know "A World of Fish" sells them in the UK (on Ebay), and he has been very good to do business with when I've bought fish food etc.

cheers Darrel

[Mol_PMB]

Thanks Darrel.

I have collected some more oak and beech leaves and will spend this evening washing, drying and storing them for the coming season. I'll boil up the tatty leaves to make some 'Orinoco tea' as well, and use some of that at the next water change for this tank to add some tannins. I'll go looking for alder cones this weekend. I'd prefer to collect them myself if I can but thanks for the enay suggestion too.

I'm hoping the fish will improve as a consequence of one of the changes I've made, and I will update this thread when I have some more news.

For now, here's a nice photo of two of my C.oiapoquensis when I first got them over 2 years ago. I really hope I can get them back to this condition.

Cheers, Paul

[Mol_PMB]

I have increased the frequency of water changes and also increased feeding a little and treated them to some live Grindal worms in addition to the usual variety of pellets and frozen.
Yesterday I did a water change with tannin-stained water (from boiling fallen oak and beech leaves). Conductivity now down to 210us.
The fish became more active than before; I'm not sure if this was caused by the change in water chemistry or the fact that the light doesn't penetrate so well through the brown water, so maybe they feel less exposed.
I'll do another water change on Saturday with some more brown water and see where we go from there.
I'll probably also get some more Corydoras for this tank on Saturday but they will initially go into QT.

[josecatala]

Hello everyone,

I am having the same issue in one of my tanks. I currently have 9 tanks running with fish and all have cories in them. Just my one tank, 72 gallon, is having this problem. I have 7 green/bronze cories and 2 Sterbai. One of the Sterbai has it really bad, where most of his tail is gone. Most have the barbles really short. I've tried several meds for fin and tail rot, but nothing seems to get rid of it all together. None of the other tanks are having fin and tail rot issues.

this tank has been running for almost 2 years. Sand bottom, driftwood and some rocks. Fully planted. I dose daily with seachem's excel, and Iron. Every third day seachem's flourish, and twice a week, seachem's potassium. Temp is around 80 F. I am pretty religious on the water changes. R/O conditioned back with Discus trace. 20% weekly.

I'm very interested to see what you try and if its successful.

[Mol_PMB]

Thanks - that's really interesting. It seems like there's some combination of parameters that doesn't work well with Cories. Hoops fully we can understand it and do better with them in future.

[Mol_PMB]

Well, I'm doing 3x30% water changes a week on the tank now, and adding tannins from oak or beech leaves, or alder cones.
I'm also feeding a bit more frequently with smaller foods, plenty of live grindal worms, bloodworms etc.

I bought some new fish for this tank on Saturday; a group of 5 juvenile locally-bred Cory oiapoquensis (which are in the QT) and there was just one wild-caught Cory amapaensis available. I bought that too because it (he?) was a beauty, and he's gone straight into the Oiapoque tank because he was 3 times the size of the young oiapoquensis.

Since the changes in water parameters I have noticed much more activity in the tank which I hope is a good sign.

There hasn't yet been a noticeable improvement in the fins of the oiapoquensis but I hope they will improve.

[Mol_PMB]

An update:
I have been doing 30% water changes twice a week (instead of once a week) and adding tannins, leaves and alder cones. I've been feeding more heavily too, continuing with a mixture of pellet, frozen and live foods.
I adjusted the filter pipework so that the velocity and noise has been reduced although the flow rate remains the same.
I've added the 5 new small C.oiapoquensis and the solitary adult C.amapaensis.
I have been adding a dose of Melafix at alternate water changes. I have reduced the additions of plant fertiliser.
All the fish seem to be doing well with some regrowth of damaged fins, though they're not all perfect yet.
Perhaps linked to the increased feeding, there is an increase in brown detritus, sometimes suspended in the water. I've been doing my best to siphon this up at water changes.
There has been an increase in the 'playfulness' of the fish, with groups chasing each other around. This usually happens with groups of one species but sometimes with more than one species. The C.amapaensis seems well at home with the 3 C.condiscipulus; though of course I wish I could get more of both! The 5 small C.oiapoquensis have visibly grown over the last few weeks and are playing with their elder brethren.

[TwoTankAmin]

A couple of quick thoughts here. I agree with those saying nitrates are likely not the issue for the reasons mentioned. I think the problem is a bacterial one. I have found fin rot usually either has fungal or bacterial cause and often both will be present. But in the case of fungus you can clearly see that component. The problem is where you live and what that means for the availability of meds.

The fact that the fin rot is persistent argues to me that the cause must also be persistent. Melafix, imo, is useless for this sort of situation. I am not sure what to suggest as it is not easy to get real fish meds in the UK. Here I would try a round of an antibiotic such as Erythromycin which is one of several I keep in my fish medicine kit. I have never had issues with it harming the biological filter in tanks, especially in a decently planted tank.

One note re Rooibos tea. This stuff is great, it will stain your water like tannins, it will release some very beneficial chemicals but it will not release much in the way of tannins. It is not actually a tea. Rooibos comes from the plant, Aspalathus linearis, a legume in the family Fabaceae- it is related to peas and beans. For fish keeping we are interested in the plant phenolic compounds which act as antioxidants and also as antibacterials (it doesn’t harm filters). This is similar to the humic acids found in natural “tea” stained waters which have similar phenolics. Oak leaves contain a lot of the plant phenolic quercetin (derived from the Latin name for the oak tree, Quercus robur) and rooibos also contains some quercetin plus the compound aspalathin, which is closely related to quercetin.

Rooibos will not lower pH nor soften water. it may actually bump your pH .1 or so. I have used it as part of a mix of things in a tank for wild Altum angels which includes IAL, alder cones and occasionally some peat. I have actually tried using rooibos as a med with mixed results. The nice thing about rooibos is you can brew it and then pour it into a tank. A lot less messy than the other things, BTW, rooibos is a popular tea for people and it has health benefits for us as well. I have not tried it however.

[Mol_PMB]

Thanks TTA for the detailed suggestions - that's a good tip and I'll try the Rooibos.