I just noticed this on my Rainbowfish. I am wondering if anybody can identify it.

Tank Size: 75 Gallon Planted Freshwater tank
Water Parameter: 0 Nitrite and Ammonia, 20 Nitrate, PH 7.8 using API test strips
Set up: 5 Years
Tankmates: 6 Angelfish, 3 Clown Loaches, 3 Other Rainbows, tetras, swordtails. No new tankmates or plants in the past 3 months.
Filtration: Aquaclear 110
Water Changes: 50% weekly
Feeding: Fish are fed 2 times per day with 1 day skipped per week. Items include algae wafers, flakes, pellets, daphnia.

Tank Size: 75 Gallon Planted Freshwater tank
Water Parameter: 0 Nitrite and Ammonia, 20 Nitrate, PH 7.8 using API test strips
Set up: 5 Years
Tankmates: 6 Angelfish, 3 Clown Loaches, 3 Other Rainbows, tetras, swordtails. No new tankmates or plants in the past 3 months.
Filtration: Aquaclear 110
Water Changes: 50% weekly
Feeding: Fish are fed 2 times per day with 1 day skipped per week. Items include algae wafers, flakes, pellets, daphnia.