Now that I have had several RTC for over 2 years, I am hooked. I really do find them to be fascinating.
What I find to be interesting is that when they are young, they are quite territorial. Once they become bigger, after the first year, they mellow out a bit.
I do keep mine with larger fish. All of the extras in the tank are disposable. Oscars, plecos, what ever is in there... they are also sized so they can be food if need be. I am not upset anymore when one of my RTC eats a tank mate. It is quite odd though when they do decide to have a snack who they chose. Usually not the smallest.
One of the things I have found fascinating is how my largest RTC has picked up a "friend" I had been given a black shark as a feeder. For nearly 2 years the black shark and "Bad Cat" have been buddies. Even sleeping together. Black sharks usually hate all catfish and will harass or even kill smaller catfish. These 2 seem to like the company.
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Others are not so lucky...
Bad Cat, when only 7 inches in length killed and ate my 13 inch silver Asian Arowana... that and after several other tank mates becoming food... gave Bad Cat is name.
After that, I stopped caring.
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Typical result of actually bothering Bad Cat inside the tank... Bad Cat having lunch.
I do not feed them every day, usually food is every 3 to 5 days. And not a huge meal, enough to see the lump. This keeps them happy and active.
For me, 30 percent water changes once a week and triple the "recommend" filtration on each one of their tanks seems to be doing the trick quite nicely.