75gal salt questions

[Diesel84]

So I have had my tank set up for about 4 months. I have 2 HOB marine land filters, a 280 and a 400 and have never been able to keep nitrates in check. Always at 40 even after water changes and cleaning. I can't drill my tank as its already set up, but is there a way to make a sump work, or can I remove the tops of the filters, light them up and make 2 mini refugiums with macro algae? Any help would be awesome

 

[Thumper828]

Have you looked into Seachem Purigen?

 

[Diesel84]

I hadn't until now. However I would like to be able to grow pods at some point as a mandarin would look awesome in my tank. Still leaning towards hob fuge, and a skimmer to compliment it.