Peacock Cichlids in 40, Kribs in a 20, and some German blue rams in another 20(yes I know the water chemistry will have to be different)Cool beans, what are you breeding? I've yet to see someone start a breeding setup with half a dozen tanks and downsize from there, wishing they'd bought a smaller pump. In a year or so you'll have 9, maybe 12 tanks, and be wishing you had more pump. You may be hatching brine shrimp, requiring another air line. These are pretty standard for a smaller setup, probably take you up to 20 devices; Amazon.com: Danner 04520 1700CUIN AP-20 Pond Air Pump with Diffuser: Patio, Lawn & Garden
Pick up one of these with the amount of outlets you anticipate needing; Aquarium Air System Valve Manifold
You can look at the wattage of a pump, and ballpark one watt per device. That AP20 will pull 20 watts, though that's with a lot of back pressure, you always want to bleed off excess air, keep that in mind when designing an air system. The larger pumps do run quite quiet compared to the little Whispers & such, I've got that AP20 & a couple chrome manifolds as a backup. I've run it on & off for projects outside the fishroom, the design has a nice little handle for picking it up. I run an Alita AL80 as my main pump in the fishroom, as the number suggests, 80w, 80 outlets. I've got a line on a used AL60, most likely get that early next year for setting up a sorting area outside the fishroom.
Everyone starts with the smaller pumps, expands, buys one or two more, expands.... looks at what they spent & wishes they had gotten one larger pump. I did, friends did, the old guys long ago who told me just buy one decent pump & be done with it did. You get an amazing volume of air out of the larger pumps, once you crank up a box filter with floss & watch it filter as well as a hob or canister filter you'll wonder why folks with multiple tanks ever run those. Everything from 1 bubble per second fry tanks to what visually amounts to boiling water out of a tank, one system, one pump, one finger on a lever.