75 gallon stocking

[petluvr]

Wait what? Nitrates and ph are a great indication of when/how much water needs to be changed. Weekly or less is a great idea, but with low stocking levels and good buffering might be able to go weeks and be ok.

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PH means absolutely nothing that isn't an indicator of anything.

 

[rufioman]

Oxygen levels in your water are more vital than anything your testing kit will tell you. Sorry if I sounded short earlier, I'm a goofy dude and come across as cross sometimes. You change your water for two purposes; to reduce harmful toxins and replace oxygen. Your kit will tell you when it is time, sure, but that shouldn't ever be a necessity. Again, sorry if I sounded rude.

 

[MilitantPotato]

Except ph will crash over time due to kh being used up by filter bacteria creating acidic byproducts.

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[SnakeIce]

More of a concern with cichlids is their growth inhibiting hormones they produce. Even if waste is low enough changing water more often keeps them from stunting.

 

[OrQidz]

I second pearl gouramis, also moonlight gouramis get 6-7 inches and can be gorgeous. Angelfish are great, you could have more than 2 but they do pair off and spawn and get aggressive. Does it have to be "a" centerpiece fish? You could do with a group of some of the rainbowfish that get decent sized, or some roseline sharks/denisons barbs that get to a pretty good size.