I believe every tank needs a few nerites, because they are awesome snails just in appearance, and then combined with their algae destroying abilities.........
I think one of these per 3 gallons makes for a good number.....I only wish that they would breed in freshwater so that I could have hundreds in my 75
I love my zebra nerites. They keep my 2 5 gallon tanks spotless. My anubias in both tanks continually get covered in brown diatoms, and then the nerites find it and clean it off completely. I have a weekly cycle in my tank of the anubias gradually getting browner and browner and then the nerites cleaning it again. Without them my tanks would be covered in algae. They really are the best algae eaters and I can't think of any that could do better in a small tank.
Yup they make the acrylic permanently cloudy over time with little mouth patterns. I should take a pic of what one nerite did over the course of a year. That's why I'll be upgrading my tanks to glass whenever I can.
Seems like any critter strong enough to scrape hard green algae is sadly strong enough to permanently damage acrylic.