New setup

Hi , I'm in the process of starting an marine tank again , size 1800 x 700 x 700 and the sump is about 1200 x 600 x 600 with 4 chambers , one is for the top up . I would like to know what size return bump to use and the size/flow of the wave makers .

Please give me some advice .

Welcome to the forums. Good luck on your journey and always remember patience and knowledge will keep you thriving in this wonderful hobby.

Now to the question.

Firstly, return pump system and wavemakers are two different systems within the reef aquarium. I'm personally a fan of high sump turnover so i have a 3500l/h pump on a 200l DT. On your tank i would probably go with a 6000l/h'ish DC pump or something.
As for wavemaker, for your size tank, 3-4 RW-15 pumps should stir things up quite nicely.

Return pump, depends on your filtration option.
If DSB and on the width of your sump I would go with a pump that delivers 4000L/h into your display. NOTE. This is after head height and back pressure being taken into account.

Wavemakers, depends a lot on your choice of corals and a bit on the rock stack formation. 20 to 40 times turn over for softies is fine, up to 60 to 80 times turnover for SPS corals.

Thanks a lot , sorry for the late reply , was out of town . The info should help me get the right size pumps .