I also have a 5.5g tank. I wouldn't suggest hc Cuba with diy co2 (unstable and will get algae) excel is not real co2. So I would avoid if Cuba unless you go pressurized. Repens should be ok if your dosing some fertz, ar mini and blyxa will be fine. I don't use co2 or dose anything in this tank since it's my Taiwan bee breeding tank.
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