What's wrong with my texas?

[RD.]

It's easy enough to compromise between the two, simply drop the temp a few degrees, say 77-78F. All of your fish will do just fine at that temp. The fact that a fish can be kept at 68-72F, doesn't mean that it has to be. Just keep the water pristine, low nitrates, no nitrites, and monitor the aggression in the tank. Stress from aggression will cause a lot more issues than ones tank being lower or higher by a few, or even several degrees.

 

[duanes]

I agree that a compromise can easily work.
But here is my reasoning for trying to mimic nature.
All fish (all living things ) have an optimum living range, some narrow, some wide, some fluctuate wildly, some don't.
About 25 years ago I started keeping Gymnogeophagus, and the first couple tries failed.
Why, because they have evolved to live in a climate where there are winter cool downs, and summer heat, the cool down rests, serve to rejuvenate these Uruguayan species.
At constant temps these species seemed prone to disease, and fungal infections.
Texas,and northern Mexico are not like Brazil, in fact there are winter cool downs and summer heat waves,
the water parameters there tend to be high mineral, high pH 8 (sometimes above), whereas Brazil waters tend to be neutral ph to slightly acidic, or in some place, very acidic, with very constant temps.
My reasoning is not to buck a few million years of evolution.
Sometimes the effects of not providing normal conditions not immediately obvious, take oscars raised in hard, nitrate rich water that seem to magically acquire HLLE for no apparent reason.

 

[RD.]

I agree, Duane, at least to an extent. Some species of fish, including many in the Gymnogeophagus family will be healthier long term when going through a cooling down period. Other species require pristine water quality, more so than other species. Some require warmer temps than others, the list goes on and on. At the same time many species can easily adjust to warmer water, cooler water, higher or lower pH values, etc-etc.

But I suspect that in this case it's not the warmer temp that's causing issues with his Texas, nor is it the pH value. Something else is going on, signs of nitrite seems to point in a completely different direction with regards to water quality, as in the OP's bio-bacteria are not keeping up with the bio-load.

 

[neutrino]

Nitrite should always be zero. If it isn't it's apparent this would be the first issue to address (or one of the first if there's another obvious problem). Nitrite causes blood problems in fish and low level nitrite can reportedly cause fin rot. Obvious or basic questions: Were any of these fish added recently? Have you made other recent changes to the tank or filtration? Anything involving filter media? How do you maintain your filters, do you replace media or rinse it out, if so what kind of water? What kind of substrate? Any meds recently? pH jumping around?

For a start I'd lighten up feeding, siphon substrate if it's gravel and that hasn't been done regularly or for a while; if it's sand, test siphon to see how dirty or clean it is-- these are just basic steps if you have a temporary cycling issue. Salt (sodium chloride, whether as aquarium salt, canning salt, etc.) is supposed to help nitrite poisoning, though I haven't dealt with that issue personally. If the tank has been running a while with zero ammonia and nitrite, then something's gone out of whack with your cycle. It may be something you can identify and fix directly or it may be a matter of feeding lightly, keeping things clean and allowing your bio-media to rebalance your tank.