Sump help

[makana]

I bought a used setup and am looking for help with the sump.

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The sump is an old wet/dry filter. The first chamber is an obvious detritus trap. I was thinking of cutting away most of the first chamber baffle and putting a new baffle around the area of the current wet/dry baffle. I'd like to keep the water a little higher so I can grow cheato in that chamber as well. I would like to add a section for a skimmer if possible. I'm not sure how to make sure I have enough empty space so it doesn't overflow when the pump is off.

Any suggestions.