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I'm having a hard time keeping catfish in my 20gal tank -- otos and bronze corys don't seem to last very long. I currenlty have only one cory (and 4 zebra danios, 4 cherry barbs, and 3 var. platys). I lost one cory last week - was laying on his back on the
bottom - when I went to scoop him, he swam off -- was swimming erratically and having a hard time -- I euthanized him.

Now my other cory is showing similar behavior-- was spending alot of time at the surface this morning and then was laying on his back -- left him and an hour or so later seemed fine -- swimming normally. I did a 10% water change last night (and had done 10% 2 days before). My ammonia and nitrites test 0 and nitrates may be high (since my tap water is about 13ppm).

Any help appreciated.
-Deb S. (in Massachusetts, USA)

hm...nitrites are supposedly more letal than nitrates...so...how long has the tank been set up for?? Did u put any medication in the tank?? If u have previously, the medication might have destroyed the bacteria residing in your filter media, and perhaps your tank is lacking in IMPORTANT biological filtration.

my nitrites test at 0 and I haven't medicated the tank -- just salt (my lfs recommended
that I add a large amount a few weeks ago -- if it was the salt, wouldn't it have killed
the corys sooner?)

this morning, he was laying upside down on the bottom, looking very dead. I went to scoop him and he swam off -- when I left home, he was resting on the bottom - breathing but not looking too great. His barbels appear to be virtually gone...

I'm very disappointed about not being able to keep catfish -- my tank has fake plants but I'm hoping to introduce some real ones soon -- after the plants are established, maybe I'll try cats again...

Barbels are gone??

that could only mean one thing.... your gravel is too sharp and has caused considerable damage to the cory's barbels and this could lead to bacterial infection and other problems....

Do check the gravel and change them if they are indeed the problem area....

If the barbels deteriorated that rapidly, then it's a sure sign that high nitrates are to blame.

the barbels didn't deteriorate very rapidly -- slowly over time so I suspect it was probably my gravel. My nitrates are around 30 ppm -- my incoming water is about 13
so I can't do much to get them alot lower.

Another clue to all this may be the key -- a few weeks ago my LFS recommended I add alot of salt (like 4x recommended dose) to my tank to help out a suffering platy.
I did add about 12 Tablespoons -- would this have a long term effect on the corys
or would they have died right away from this ridiculously high dose. (I no longer
take advice from that LFS...)

The salt could have had an effect in the corys as some cories are very sensitive to salinity. Check the gravel. Is it round gravel or sharp gravel. You mentioned a sick platy what did it have?

Sorry about all the questions just tryin' to help

My gravel is not very smooth -- probably a bit rough for corys.
No idea what the platy had -- it was swimming around with clamped fins
for a few weeks and seemed quite lethargic -- no one else in the tank
seemed to be sick then...

Most catfishes are VERY sensitive to salinity. So i suspect that your addition of salt to the tank is the main culprit in this instance. A good way of checking your gravel for sharp edges is running your hand/palm through the gravel. This way, you can feel for any sharp edges in the gravel or not. Another way is to inspect them closely. In my experience, when i look at round gravel, they should look like those which have just been worn off, and very rounded.

while sharp gravel will wear down cory barbles, i have found high nitrates to be much worse. my gravel (flourite) is not extremely sharp, but after a week or so i found my cories had slightly shorter barbles. fortunately, they have not shown noticable erosion since and their babies are almost past the stage where they make good cory snacks, so the parents can move back in with them soon. when i was fairly new to fishkeeping, i found that when i waited until nitrates were over 40 to do water changes, the fish slowly lost their "whiskers". the addition of that much salt all at once certianly didn't help either. you are removing it with water changes, i hope?

are there any possible sources of toxins you can think of? air freshner, hairspray, cleaners, fumes etc getting near fish tanks or equipment? tank light with no glass/plastic between light and tank? metal touching the water anywhere? (or metal having condensation on it, as in the case of the tank light)

-Liz

I've read that there are different schools of thought on barbel errosion. One is harsh substrate, another is bacterial/fungal infection, and I've also read that some believe it has to do with lack of good protein in the diet, and the high nitrate suggestions here.

Food that has an opportunity to grow a moldy look to it is not good for them. I brought 3 agasizzii's home with shorter barbels and I made sure I gravel vac'd more regular. I do 1/3 tank weekly and the filter on week 4. I also picked up sinking shrimp pellets and also make sure they get occassional mosquito larvae. I can't believe how their barbels have grown.

Because of other symptoms along with eroded barbels, it makes me wonder about infection. Can you see any reddening anwhere when they are dying (base of pec fins, underside)?

I agree with above on salt. Why add salt - I'd slowly ween that down slowly so its a happy medium between needs of molly and cories.

Here is a link to one article on barbel errosion - you can search the net for more... just scroll down to the heading on that topic:

http://www.skepticalaquarist.com/catfish.html

Unfortunately, my last cory died last night -- he was hanging in there for a while and I had high hopes that he'd make it but it wasn't meant to be.

So I've been doing water changes to reduce the salt level in my tank--it is currently down to about 5 Tablespoons (in a 20 gallon) and I'll continue to do water changes to get it lower. My hope is to convert the rough gravel in my tank to a smoother substrate and also add live plants (after I get the salt lower) and then try a few more corys (since I do love them!)

What is a good substrate? I'd prefer to have a darker substrate so straight Silica Sand wouldn't be ideal. I was looking at Onyx Sand but can't tell how rough it is. I was also looking at Tropic Isle Tahitian Moon but one online seller said it will not affect pH and another said it will buffer to 8.2. My pH is already on the high side (7.6-7. so I don't want to send it any higher. Thanks for all the suggestions and thanks in advance for any substrate suggestions.
-Deb S.

So sorry to hear that Deb. I think you're doing the right thing in lowering your salt. Its funny how those "community" tanks become a balancing act, in your case a Molly's like of salt and the cory's dislike of it.

I hope you'll try again later when you get your tank the way you want it. Cories are one of my favorite fish, tho they do take a lot of catnaps *lol*.

Keep an eye on ammonia and nitrite regular before adding any just to be sure as they are more sensitive. Meds too.

Aqua-colista sand is neutral and does not affect pH.. so could you find that??

OR the Dennerle gravel, for planting purposes.... Plants normally do not take well to fine sand...