55g sump design need advice...

[Flusher]

Looks good. Here's my input:

Make the first, second, and fourth baffles lower (from the left; the baffles coming up from the bottom). Sumps usually run only at about half full. The sump would have to be almost full for the water to make it over the baffles.

Make the first and last chambers smaller so you can have a bigger refugium. Put the skimmer in the first compartment.

The baffles are to reduce bubbles from the skimmer moreso than the incoming water, IME, so there's no sense putting the skimmer after all the baffles. If you put the skimmer in the left-most compartment, put three baffles like those dividing the middle and right compartments.

The baffles should be fairly close together, maybe 1/2" to 1". (I could be wrong. Get a second opinion. )

Forget the bioballs. Most people, from what I've gathered, consider them to be a nitrate trap in a reef tank.

HTH
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Zx14 vs hayabusa