nitrates kill fish.
if there is too much "fertilizer" in there, the fish will die.
well, unless its one bad ass fish
when you set up an aquarium and want it successful (the fish to live)
you first set up the bacteria in it
which eats waste and turns it into less harmful waste (and more accessible to plants)
dumping a fish into just some fertilized water.
is probably going to harm or kill the fish.
first of, you added ferts, (deadly to fish in too large doses)
and then the fish is gonna shit.
and you wont have any bacteria to speak off.
though if you have plenty of plants sucking off the waste, the fish should be allright.
but one fish probably wont make that much fertilizer.
plus you´d have to add micronutes anyway, stuff like iron and whatnot. (unless your fish has a nice varied diet.)
so the waste is just going to build.
eventually probably killing the fish.
