Losing Cory's like crazy

[originalhandy]

So Friday I came home and one of my full grown emerald corys was dead, all looked fine then I saw a peppered cory floating. Did a 50pc water change.

Saturday morning another cory is dead so I do a 50pc change too.

This morning a juli cory is dead, also a neon tetra.

Ammonia tested a few minutes ago 0, Nitrates 0, Nitrites 0.

I started dosing 2 caps of Excel every two days since last Sat though I stopped on Wed as Friday would have been the next day to dose but a fish was dead so I stopped.

Whats new, added 3 cory two weeks ago, Julis. Added an Amazon Sword on Thursday. Also added the plant below on Thursday, dunno the name. I left the band tieing them together on it, that shouldn't hurt should it?


Added new disc food on Thursday also. The shop buys in bulk and feeds it to his fish. He packages it for resale so I doubt thats it just stating what's new.

Temperature is 78F in the tank.

All fish (including corys but they did before they died too) look good swinming around and are great colour (GBR usually darken when not doing well).

Any ideas, pointers would be great. I love my corys ans hate losing them, especially the peppered that has been in the tank from day 1.

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[mnemenoi]

Hmm, the weight is no big deal, you have Cabomba. I'd double check your Nitrates. You should have something registering. Shake the 2 bottles and tap them for a few minutes each and test again. A part of the testing agent solidifies and gives a false reading. Nitrates would be my suspicion, though until I can see the numbers I'm not positive. I'd stop Excel dosing for now. Sorry to hear about your losses. I have a devil of a time with corydoras....

[originalhandy]

Ill retest later, they've showed 0 since the tank was about 6 months old. As I just did a water change I'll try later though.

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[mnemenoi]

We occasionally get a 0 Nitrate in our densely planted shrimp tanks that are fed every other day a teeny bit, but most tanks should register something, even if its crazy low like a 10

[originalhandy]

Lost two more, water results are the same. Should I try some meds ? Melafix or something?

My other bottom feeders are fine, albino cory, eel etc.

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[gambs]

How old is the test kit.

[originalhandy]

Its less than a year old

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[gambs]

Might be getting false reading on nitrate.

[originalhandy]

Its always been that, even at petco and petsmart testing it except for the time I used Algaefix and my tank crashed. Ill have em check later again to see if they read different.

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[mnemenoi]

Are you using test strips? They are notoriously awful with incorrect readings. I'd suggest grabbing a Freshwater Master Kit, the API Nitrate test reagents can settle a bit and need a vigorous and aggressive shaking, but do work well. 0 Nitrates in a tank with any significant bioload and daily feeding is almost unheard of. In a high tech tank it can happen, but then you need to start dosing Nitrates to supply the plants due to their increased growth rates. Most Corydoras/tetras have been very touchy when it comes to Nitrates in my exp. anything above a 40ppm and they begin to act up and just seem to die off unexplainably. Usually 40 ppm might be a tad bit high, but many species don't even react until they get above 100ppm. With the water change prior it does seem weird, but I have done similar things and they have died afterwards when the parameters swung back into better numbers. Perhaps it is just a poisoning they are unable to fight off. Let us know what you find out and hopefully we can get to the bottom of the issue

[originalhandy]

Im using the Freshwater Master Kit. I tested today, got 0 across the board. If Nitrates are anything they're bearly reading, they're not above 5 or anything. With test strips at Petco & Petsmart they got same readings I did. I could be convinced they where slightly above 0 looking at their strips.

With plants I do use a root tab, one a month at the roots of each plant. Do I need more? They affect nitrates, don't they ?

I am at a guessing game right now.
1) some sort of infection in the gravel ? Cause they're bottom feeders they got it ?
2) A sick fish died from something and they got sick from it
3) The new disc food I am using, though the albino bn plecos are fine.

I put in 3 caps of Melafix, 75G tank. Do I need to do that daily?

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[mnemenoi]

Hmm, to be honest it all sounds correct. I am also at a loss to determine a cause. With no obvious wounds or issues, I'd guess either a parameter (which we have ruled out), temperature (assume its correct), food source (with everything else eating fine seems unlikely), or bacterial (could be possible, but it would wipe out all of them and not just a few). None seem to fit the bill and account for all the parameters and the manner in which they died. I'd slow down dosing and just monitor the tank. I hate dosing with no clear indication of what you are trying to correct. Melafix and Pimafix are skin condition medications to promote repairs and inhibit infections. With no discernible lesions or inflammation I think its dosing just to dose something. I could see maybe dosing an antibiotic, but with no more showing symptoms I am not sure if wiping out your bacterial colony is worth the risk. Hate to recommend doing nothing, but given your info, I don't see a justifiable medication that would help until we can determine your causation.

[originalhandy]

Lost another one last night. I have two eels in the tank, I see them once in a while. If one is dead, is there such thing as it being toxic when its dead and they fed on it ? I know there is such thing with a fish in saltwater, just clutching at straws really ...

[DoubleDutch]

Could the plant be treated with some kind snail-poisson as done overhere sometimes. Mostly shrimp are the victims of that.

[Fancyfish]

What are the other tank inhabitants? I see what looks like an Angelfish and tetras. You mention you have eels as well. I wonder if you have a pair of fish getting ready to spawn or protecting a spawn.

another question, what do the fish look like when they are dead? Do they have open wounds, red streaks, are they bloated other than would be normal from death? Have you cut any open? Maybe you have an internal parasite or maybe there are open sores inside the fish.

Since you are losing them one or 2 at a time over a period of time, I bet there is some aggression in the tank from some other critter who doesn't like the corys messing around at night.