I had a 30 gallon tank nitrates were near 0 (bio balls and all) only had 2 medium and 2 small fish. I upgraded to a 75 and transferred everything over except the trickle filter, I went with an Eshopps 100 with the same bio balls.
Two months later my nitrates were 40ppm. I was stumped until the overflow box backed up from the sponge being clogged. Well I now rinse the sponge in the overflow box twice a week. The tank is now eight months old and the nitrates are steady at 2.5ppm
Sometimes its the simplest things.
I would add more rock, larger skimmer, make sure your sump has enough flow, rinse and clean everything in RO water weekly and maybe you need a refugium to lower those nitrates.
PS. no more fish
Two months later my nitrates were 40ppm. I was stumped until the overflow box backed up from the sponge being clogged. Well I now rinse the sponge in the overflow box twice a week. The tank is now eight months old and the nitrates are steady at 2.5ppm
Sometimes its the simplest things.
I would add more rock, larger skimmer, make sure your sump has enough flow, rinse and clean everything in RO water weekly and maybe you need a refugium to lower those nitrates.
PS. no more fish