Who Gives A Fish Forums

My Anubias roots are turning black and I'm not sure why. The tank is a 20 gallon with Fluval Stratum substrate, LED lighting for 8 hours a day, and a sponge filter. Water params are good, 0 ammonia, 0 nitrite, 10 nitrate. I dose Seachem Flourish once a week. Any ideas?

My tank's a 40 breeder with soft corals. I use a single Nero 3 at 30% and they're fine. Maybe your MP40s are overkill for a 75 with softies.