Mysterious tank problem- any thoughts appreciated!

[Jazz]

I am the steward of a 55g community tank ( yes, I know it's small. We will upgrade to larger tank when we finish home reno). I have a mystery that is killing fish. Not sure what info is relevant - I'll try to keep it brief while providing enough background. This may be long. Feel free to ask for more details if I have left out important stats. It was an established tank given to me by friends in October of 2006. We are polar opposites in aqaurium care and closely monitor tank conditions, etc. Tank came with 1/2 dozen albino cories, bala shark (4"), rainbow shark, . We have added over time 3 discus, 2 pictus cats, a 2nd catfish of unknown type, and some clown loaches ( about 6 small). Despite cramped quarters, our fish hyave flourished, get along beautifully and aside from the occasional ph issue ( acidic side) and ammonia buildup ( rarely an issue due to the frequent partial water changes appreciated by the discus and increased filtration) have had no tank health issues . Bacterial balance has been good. We use filtered (reverse-osmosis) water in tank. We have a biowheel filter, a standard whisper filter, an undergravel filter with powerhead, and use sponge media as well. The tank has been largely self-sufficient with what we felt was a good mix of polluters and pollution eaters. Until we went on vacation for 4 days. We had what we thought was a well- advised friend come by and feed 2x per day ( we divied out amount) and turn lights on and off. When we got back we could not find one of the pictus cats anywhere in tank. assumed he might have died and his remains eaten before they were noted. Within a few days, we lost a clown loach, and then an albino cory. We started to become concerned and did a more rigorous tank cleaning during which we discovered the missing pictus cat- his decaying body was in a hollow log behind a knot so as not visible. The clown loaches were definitely feeding on the carcass. Tests showed wtare levels all out of wack with ammonia through the roof ( i assume because of decaying matter)We thoroughly cleaned tank, did a 20%water change, used ammonia blocker, changed all filter cartridges ( except biowheel wheel). Levels gradually returned to similar to usual but over the next few agaonizing days all bottom feeders/scaleless fish not transferred to another tank died. Except for unkown cat ( "BEN"). The discus and bala shark were unaffected. Spoke to LFS guru who surmised it likely some sort of heavy metal contamination (perhaps suntan lotion on fingers got into tank, etc) therefore affecting sacleless fish but not otherwise sensitive discus. Without a way to test for this, he advise use of a poly filter to pull out contaminants. which we used for 24 hours and removed. Frequent partial water changes, cleanings, etc.. As a regrettable means of testing we put albino cory from another healthy tank into this one- it died within a few hours. Discus still seemingly fine. Ben seemed fine. More water changes, etc. two weeks later Ben develops rapidly spreading ulceration and dies. Seems to be pattern of labored respiration and graying eyes in dying fish but this was the only fish to manifest other outward signs. More cleaning, condition monitoring, more time passes, add albino cory and a small bala shark ( added bala to add something that wasn't scaleless and hopefully immune to cheer up spastic adult bala). Had to remove cory within 5-10 minutes due to looking pekid- perked up in healthy tank and survived. Bala died within 45 minutes. No one in local fish community seems to have any ideas. I am concerned because what must be diluted concentrations of supposed contaminant after cleanings and water changes have not led to less or slower fish kill.In fact the opposite is true. Scaled fish have been unaffected until bala died and then today when one discus has cloudy eye (related?). I have no idea how to address the matter, what I can test for if anything and am concerned that there is invisible damage ocurring to discus. Does anyone have any ideas? I feel the clock ticking.

[Rue]

What are your nitrite and nitrate levels?

Your tank was rather overstocked...I suppose the dead fish might have been just enough to totally push the water parametres over the edge...I'm not sure though why your fish continue to die with all the water changes you're doing...

Ammonia blocker isn't really something that works all that well...most 'quick fixes' don't I find...

[nanaglen2001]

Dont think that Nitrate or Nitrit have anything to do with this catastrophy at all...he did lots of waterchanges, remember....

May I copy your post to translate it into german. Maybe some folks and friends in my german forums have an idea.

Did you introduce some new decoration into your tank before you left for your holidays? That healthy tank, is the same water in it? My guess is going direction intoxication. Have you got life plants in your tank?? Anything that can rot, which you didnt remove, cause you didnt notice it yet. Rotting roots can be disastrous to a fish poulation.

[Jazz]

Thanks for the quick response. Nitrite and nitrate levels were somewhat elevated when dead pictus cat was discovered but since have been within the same range as they have since tank finished cycling. I will be doing tests again tonight and will give results. I only used the ammonia block as an emergency precaution. I know the best defense is maintaining good water conditions from the start which we have ( or thought so). Thanks again for your thoughts.

[Jazz]

I'm no expert but I tend to believe the intoxication theory to be most likely as I think nitrate/trite levels would also be affecting discus equally as they are incredibly sensitive. This problem has only affected scaleless bottomfeeders with exception of the juvie bala shark. No, we did not add anything new to tank but I do wonder whether a couple of decorative items purchased at LFS might have toxic paint underneath a clearcoat and now maybe the clearcoat has worn thru and leaching is occurring? Just a theory but we did just pull a couple of possible suspects from tank anyway. Healthy tank has water from same source in it. No live plants in tank. Please feel free to cross post anywhere as needed. I very much appreciate your help.

[Chrona]

I agree with Jazz, though I think you need to do much larger (50%+) water changes to remove the nitrites and ammonia (and whatever the toxic mystery substance is) in the meantime. 20% really doesn't do much (bringing say 5 ppm ammonia to 4 ppm).

[Lady Hobbs]

You mentioned 20% water changes. I would do much larger water changes with the stock you have. Partically discus who require large water changes.

I'm also curious if you use pure RO water. Generally RO has to be supplimented with just tap water or suppliments added because so many nutrients are removed with the RO.

I have a feeling perhaps your fish were overfed and along with the dead fish in the tank, you had an ammonia spike. You have the ammonia eating bacteria that may have removed signs of it in a short time but this still lead to the nitrites and nitrates.

You also didn't mention how high your nitrates are. They should not be allowed to go over 20 and preferrably, closer to 5 or 10.

[Jazz]

Thanks for your thoughts. The discus geeks I know ( i say this with the utmost geek affection) advise against more than a 20% water change due to ecological disruption but I suppose oue ecology is already disrupted so 50% it is. I'll keep you posted.

[Jazz]

Thank you all so much for your thoughts- much appreciated!

I do use pure r.o. water but this has never been a problem before and my other healthy tank has no bottom-feeder issues. ?

So, before yesterday's 50% water change, my ph = 6.0 ( usually is 6.0-6.4), ammonia is .5 ( up from usual of 0-.25- i think due to no bottomfeeders to perform janitorial services). Nitrites are 0, nitrates are between 0 and 5.

Again, thanks and I'll keep you posted.

[Lady Hobbs]

You stated you usually have .25 ammonia? ANY ammonia says you are having a spike of some kind. I suspect your tank may be going thru a mini-cycle. You should always have ammonia readings of 0 and any ammonia can kill......especially with bottom feeders who do not get surface air.

Most that have RO systems use half tap and half RO. You should be using a suppliment if using all RO.

[Chrona]

If bottom feeders are required to prevent leftover food from rotting, then I think you are feeding a bit too much. If the discus are grown, then you don't need to feed them as much as juvies, so I'd cut down on it as overfeeding is probably one of the causes behind the ammonia spikes.

[Jazz]

I usually have ammoia readings of 0 and if any it is never above .25. Until the other day. However, throughout this turmoil prior readings have been as they should be. I have not seen bottom feeders as required- they have just always been a part of the ecosystem and it has been working well. But now without them there it does take a bit for everyone in the family to get a good idea of how much food to cut back. I'm better with that now.

[xoolooxunny]

he mentions changing ALL filter material except the biowheel. That could have caused the ammonia spike as it is not enough to take on the extra load it probably never had before. Whats the temperature of the tank? sorry if i read over it and didnt see it, but ive learned that higher temps = more toxic ammonia. also, have you added any salt to the tank? do you have a lot of carbon media working in that tank? I found that it can lower ph in great quantities. (i had about 2 gallons being filtered with a 10-20g filter and lowered the ph to 5.5!)

[Jazz]

Thanks xoolooxunny! I did change over some time ( not all at once) all filter media except biowheel AFTER the inception of the problem as poisoning from an outside substance was the first suspicion and I didn't want it lurking there. I suspected it might raise ammonia levels a bit even though I left time between the changes. You are probably right. The temp is high in the tank as it has been my understanding that the immune systems of the discus function better that way- 84-86 is typical. I have never used salt in the tank as I was told it would be toxic to scaleless cories. I do have some carbon media in the tank- 1 insert in the biowheel filter and two in the whisper ( both sized for 55 g tank). Is that too much? I have had a hard time suspecting so since things were so good for so long. but I may need to learn something.

[Rue]

...I use salt...my corys are fine...this group is 2 years old...my other group was about 4...

Not sure what the lifespan of corys is supposed to be though...maybe that's young?

[cocoa_pleco]

average cory lifespan is 6- 8 years i believe. They hate salt, like other cats since they have skin not scales

[Rue]

Tonic levels don't seem to hurt the corys...higher levels are a different story...

[Jazz]

Every time I try to leave a longer post the system gives me an error message so I will provide detail later but I think the problem is solved! Intoxicant, most likely lead or other heavy metal. Took apart tank and then put discus and bala in other healthy tank and moved flowerhorn to tank in question ( she's resilient- I think she could eat a hand grenade and merely burp a few times)- 24 hours + and she and her cories are doing great! Thanks to all!

[Jazz]

48 hours and all is well! Big momma (flowerhorn) and her albino entourage are doing great! I am doing another large water change just to be on the safe side. I found tiny paint particles adhered to gravel ( couldn't see them without removing gravel ) that had come off a tiny buddha statue that had been removed earlier in the week when I realized it's clear coat had come off. I think the paint contained lead or some intoxicant. No more painted decor in my tanks!

Also- I took to heart the advice about adding supplement to RO water as I will be continuing to use it- couldn't find anything at LFS. Does anyone have a specific product to suggest?

Jasmine