Guppy fry and diseases?

Question

I recently put my 3 guppy fry (1 week old) into a new tank, 5gallons, all appeared well and they were feeding on powdered flake food fine until I Liquifry 2 a food specially formulated for livebearers fry.
The next day 2 of the fry had disappeared and I assumed they'd died of a mystery condition and been sucked into the gravel by my undergravel filter. A day later whilst still looking for the missing fry I found one, immediately transferred him back into a floating box of my 10gallon aquariums water and left him, he was in a terrible state, swimming upside down and spinning.
He seems to have recovered now but today I found the other fry amongst the gravel and he too is alive and back into the other water. He has absolutely no tail though, will it grow back? He appears to be feeding and is comfortable with my other fry. The 5 gallon tank was emptied, but parametre testing showed no ammonia, trace nitrites, trace nitrates and a pH of 7. Is this finrot, if so why?

It's more than possible, since both were found in the gravel. Both of the injured fry are eating fine now, and there's no signs of agression between them that I can see, appreciate the help again MM.

Answer 1

I doubt it was fin rot that took the guppies tail. Even on a young and small guppy it would take more than a day or so for it to lose all of it's tail. I would suspect they have some type of internal bacterial disease ( that explains the poor swimming) and once your second was very weak, the other picked on him and ate away his tail.

Sometimes it's basically impossible to track the source of a disease. Many times in cases like this people will blame the water source, or bad water conditions, or some other generic "reason" that can often neither be proven nor disproven, but in all honesty it's rarely from your source of water and never the direct cause of dirty water.

There is also the possibility that all of this is caused by physical damage. The undergravel filters would pull food down into the gravel, the fry would chase it and get stuck or injured on the gravel. That can and does happen often enough that you shouldn't discount the possibility.

MM

Answer 2

Don't use liquifry, its a waste of money and only fouls your tank water. Livebearers can be easily reared on finely crushed flake food.

As for what's wrong with your guppies, could be that smaller fry are being predated on by larger ones. If your ammonia, nitrite are at 0 then it is unlikely that your fish would be getting any sort of diseases.