Danio-Possible injury

Question
Hi! you answered a question about my bent danio on Mar 5th. I put him in
isolation and treated with tetracycline, per your suggestion. I treated for 12
days, which is the limit according to the package instructions. I made water
changes between treatments and after. I have maintained the salt bath. He is
not worse but he is not better. He can swim in a twirly kind of way, but can't
seem to get his head off the bottom of the tank. Twice I have pinned a bit of
food to the bottom with a stick for a few hours to see if he could eat.  I don't
know if he ate or not. I don't think he can eat in the usual way because his
spinning would move the food away. It is also difficult to maintain water
quality in the hospital tank since it is not an established tank. Water changes
must be done with distilled water because the tap water is too high in
nitrates. I don't know what to do next. I don't see how he can survive or go
back in the main tank without improvement which looks unlikely.
The fish in the main tank remain healthy.
Thanks for the general help. I'm glad to know the real driftwood is helping
the ph. It was hard to find real wood. I don't treat for snails, I use a turkey
baster to pull them out or pick them off by hand, they're just little. I don't
remember why I didn't get a loach. Do they eat the real plants?
The fish I lost trying to increase the school all went for different reasons, like
the hachet fish who collided in their first 30 seconds in the tank. One of them
lost an eye and died instantly. There was no one reason i lost them, just a
series of unfortunate events.
Thanks again-Stefani  

Answer
Stefani:  There is a product called Finquil which is the best way to put a fish to sleep.  My best hope for your little guy was an infection  of either his swim bladder or even Fish TB.  The antibiotic has made no difference ... which tells me that his condition is caused either by a genetic factor, a physical injury, or a chemical compound such as ammonia or nitrate poisoning.  All of these possibilities are at this point in h is life untreatable.  If this were my fish I would put him to sleep. I give you all of my assurance that this process is peaceful and humane.  Again... I am truly saddened for you fish's condition... and do keep me posted... dave