Fish acting very strange, Help Needed Please

[BobCat]

I have four Prehistoric Monster Fish (T. amazonica) in a species only set-up.
My problem is that one of the fish as for the last few days, not being burying itself in the sand. It is no longer taking food and seems quite listless. Today I though it was dead and gently poked it with my feeding tongs and it slowly swam up before floating back to the sand upside down and remaining like that until I myself turned it over.
There is no signs of disease or damage to the fish and I cant figure out whats wrong. At times it appears to try and bury itself but doesn't do a very good job, and is often lop-sided.
Can these fish get stung by eachother? I wouldnt have thought so but the only theory I can come up with is that it may have come into contact with the venom of one of the other fish and is hurt that way. I really can't work it out.
I have been feeding the frozen krill but have since introduced some fry in an attempt to get him to feed again (which I dont think he has taken any off but can't be sure).

If anyone has any experience with these fish or if you have any ideas please let me know, I don't want to lose him/her.
Thanks

 

[pophead]

could you post a pic? I'm not familiar with the name "T. Amazonica", and the common name Prehistoric Monster Fish pretty much covers most fish discussed on this site, so a pic would help.
thanks!

 

[BIGgourami]

yeah i've seen them, ugliest thing in the world.
but sorry, not familiar with keeping them. it's likely that one got stung but does seem improbable. keep asking and looking elsewhere.
good luck.

 

[Lupin]

Pls post your exact water parameters, size of tank and occupants. The more details you provide, the better.

 

[pophead]

just looked the fish up, nice fish!
I've had fish act like this when they had an air bladder problem, but I'm sure that's not the only cause
hope he pulls through!

 

[BobCat]

Its a two foot tank, only occupants are the four T. Amazonica which are about 8cm long. The substrate is silver sand to a depth of 2" which is stirred and cleaned regularly. The tank is filtered via a fluval internal power filter. I'm sorry I have no pics for anyone who is unfamiliar with them but PFK has info and a pic at http://www.practicalfishkeeping.co.uk/pfk/pages/show_article.php?article_id=189

Water Parameters are Ammonia 0 Nitrite 0 and Nitrate <10

I have been very careful with water changes and am totally at a loss as to the problem, this morning I thought he was dead, lying upside down and no longer seeming to be able to keep himself the right way up now at all.
Unfortunately I now have to leave for a day, so my GF will be looking after him, but I dont suppose he has long left anyway.

Thanks for your input though guys, theres pretty much no info out there on these guys and it seems not many keep them.