Hello!Soon,I will have 800 liter (200 gal) tank. Is it ok to have Arowana,3 Oscars 2 Parrot ciclids, 1 Peacok Bass, 2 babies redtail catfish,

  • We are currently upgrading MFK. thanks! -neo
Short answer is no.

Long answer is that, before even considering compatibility and waste output, most of those fish get too big to physically fit in a tank that size (specifically the pbass, rtc, and aro). The only ones that could work long term are the senegal, jag, Oscars, and parrots.

With the remaining fish, you’ll run into issues regarding aggression and differing water parameters. A 200 gallon tank seems big, but gets very small very fast for large, aggressive cichlids. The bichirs generally play nice with most cichlids, though a sen stays small enough to potentially be food for a particularly large/hungry Oscar or jag.
If it were me, I’d pick one of the cichlids and build the tank around it.
 
The redtail catfish being part of the Pimelodidae family, there are other awesome species from this group which stay smaller and could fit in your tank.
Wouldn’t you mind giving us the dimensions of it?

If you prefer going for the bichir instead it is fine too, but then you will have to forget the catfish. Since the bichir are slow eaters they might get outcompeted, especially if you throw in an aggressive cichlid as well.
 
Even if the fish would fit, which they don't, this stock list is a little like ordering a pizza and choosing pickles, pepperoni, pineapple, eggs, bechamel sauce, strawberries and dog treats as toppings. Sure, they all sound delicious when you're hungry and checking off items on the delivery app, but not so much when your pizza arrives and you see the chaos you've created.

It's understandable to feel excited about new species and go on a stocking spree when you get a new tank, but a couple months down the line you might find that you like a couple of the fish and don't much care about the rest. It's easier to stock with just a small number of species, or even just one, and add more as your tastes develop. I thought I would like rams and apistos when I just got into the hobby, for example, but now I would not keep one if it paid me rent... nor any of the other vile, hyper-aggressive, born-evil, hell-spawned career criminals they call cichlids.

Say, maybe start with a bichir or mid-sized cichlid/catfish, see how you like it, and either change species or add compatible dithers depending on your experience?
 
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