New Fish Question

Hi All:

I have been getting diatoms on my sandbed. I do 15-20 gallon WCs every 10-14 days with RO/DI water that I make.

I have very minimal on glass or powerheads. A little on the rock. I would really like a fish that will eat it wherever it is. I skeve just about all CUCs so I prefer doing what I can with maintenance and an omniv0rous/herbivorous fish.

Any ideas? Params below.

Thanks!

Ammonia-0
Nitrite-0
Nitrate 5-20 depending
pH-8.2
Sal. 1.023-1.025 depending

92 gallon corner bow front
25 gallon sump
skimmer
3 power heads
30lbs LR
1-1.5" sandbed
UV sterilizer

2 Ocellaris clowns
3 blue/green chromis
1 cleaner shrimp
1 male purple eye/lyretail anthias and 2 females
1 red flame angel