With that size tank, and its large space you will do very well.
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That said, because GTs are extremely territorrial , even in that much space, issues may arise as they hits maturity.
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About 5 years ago, I started a 6 ft tank with a dozen wild caught Andinoacara coeruleopunctatus (GTs smaller cousin).
They did well for just about 3 years, until maturity kicked in.
As juvies they would often hunt together like a pack like wolves, to take down larger prey than themselves.
At the maturity point , someting snapped, and the most alpha of the males took out all other males, and a few unreceptive females.
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Leaving just 3 females, and himself to coexist in that 6 ft amount of space (180 galls).
I used geographically correct Tetrasas dither fish, and a couple Awaous gobies as tank mates, which were basicall ignored (no other cichlids shared the space)
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After his purge, he spawned intermittantly with the 3 females on and off for without incident years.
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Once this genus gets past the vurnerable shoaling stage, they usually become loners,
even an 8 ft tank, is a puddle compared to the spaces where I collect this species.
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Where I find them, I often find just a pair, or 2, in a stetch of river the size of a city block.
And just for reference, the Andinioacara I collect are a smaller species than A rivulatus or stalsbergi, but share th same basic attitude.