Stocking a 650 gallon South American tank

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South American 650

Feeder Fish
Apr 13, 2026
4
4
3
37
Florida
I recently purchased a 650 gallon tank. It’s 10 feet by 40 inches wide by 30 inches tall.

Below is what I’m currently looking at for a stocking.

Flagtails x7
Oscars x4
True Parrot Cichlid
Chocolate Cichlid
Electric Blue Acara x7
geophagus sveni X7
Red Shoulder severum
Golden severum
Green severum

Would this stocking work together?

Any additions or substitutions?

Any suggestions for a cat or two?
 
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I've always wanted a tank with a bunch of flagtails. Would that many work in a 10' tank? I don't know, but I'd like others' experiences.

A group of Chalceus would be cool schooling fish at the top of the water.

I'd go with one group of mid-water cichlids and one that stays closer to the bottom. And leave out the one-off's and man-made fish like electric blue acaras.

I'd go with G. altifrons over Sveni if you're going to have rough and tumble fish like oscars, Hoplarchus, or Heros.

Just my opinion
 
I would lower the number of flagtails to 4 if it were me. Flagtails can reach over a foot and you'll have some heavy hitters in there already especially with the 4 Oscars and hoplarchus psittacus.
 
I've always wanted a tank with a bunch of flagtails. Would that many work in a 10' tank? I don't know, but I'd like others' experiences.

A group of Chalceus would be cool schooling fish at the top of the water.

I'd go with one group of mid-water cichlids and one that stays closer to the bottom. And leave out the one-off's and man-made fish like electric blue acaras.

I'd go with G. altifrons over Sveni if you're going to have rough and tumble fish like oscars, Hoplarchus, or Heros.

Just my opinion
Is it a size issue with the Sveni or a temperament issues? I see the altifrons has a larger average size?

I was going with the three different Severums, the Chocolate and True parrots for some look diversity in the tank. Is having one offs like that an issue for husbandry or just personal preference.

I’ve kept fish for over 30 years everything from planted community to African cichlids to reef tanks. This will be my first tank of large South Americans. It’s also by far my largest tank I’ve had. Prior to this my largest was a 125.
 
I have a buddy that has one in a 210 and it's roughly 13-14 inches and looks almost cramped but he's had it for years. So just try and picture a full solo in a large 6ft tank, then 7 fully grown flagtails with 4 more feet added. They are pretty big not just in length, but height and thickness too. But they are beautiful though!!
 
Id send it on ur full list 💀🤘… pretty “responsible” across the board IMO… maaaaaybe 5 flagtail. U gotta have enough so u dont get one bad apple in the group. Lets b realistic tho also in that ur full list probably all isnt going to make it to adulthood. Chit happens… out of anyones control, thats life in a box. Electricity and equipment alone leads to alot of “accidents”…

Most people with a 650 “SA” tank are stuffing it full of aros, large cats, rays etc… so a lineup of pretty small fish for the footprint is again a responsible alternative.

I have a 650 and its had 5 aros over 24”at once, assorted SA cats, 32” plat redtail, 52” wels, arapaima 😬😂… none of which were really “lifers”… after 15yrs it just has 3 CK’s, 3 tinfoils and 1 silurus catfish. Very understocked but about zero maintenance at this point. Do what u want and have fun.
 
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I’d personally skip the electric variant and get the better looking original Andinoacara pulcher. They just don’t look natural in a community aquarium setting in my opinion. It’s a shame how the hobby is as Kevin from TUIC was the only dealer that I knew was selling biseriatus as these would look fantastic in a 10ft tank. Another cool option would be coeruleopunctatus as they’re still available. Not my photos.

biseriatus.
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coeruleopunctatus.
1776199642045.jpeg
 
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