I have a 20 gallon sump under my 75 and I have a sponge filter in it. The 75 also has a sponge filter.
The one in the sump is covered with these tiny little snails, while the one in the tank above is not.
![F8DA1225-2017-418E-B0C3-C71DD6C138A1.jpeg F8DA1225-2017-418E-B0C3-C71DD6C138A1.jpeg](https://www.monsterfishkeepers.com/forums/data/attachments/1244/1244219-5b93a6c1bfbdd1e8bdfb03c24101412f.jpg)
In fact, between hungry fish and frequent water changes, I have lost almost all the other snails in the system.
The funny thing is that these snails never get any larger. They are getting through a fine mesh on the overflow above, so maybe I am selecting for just the tiniest snails to survive?