Way too low ph for haps. Most of them like 8s. I bet you could find some that would live however.
You could do a ton of different bigger American cichlids. Besides price the struggle with discus is water parameters, especially with ph. If your normal tank is 6 I'd say try discus. Lots of mildy aggressive other cichlids would work too. I have a blackbelt and as Oscar with my poly living fine, had severums in there too until the blackbelt killed them. You could also go with datnoids as well.
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Not too big on cichlids.
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