lol... the eggs. I recently picked up 5 nerites for my 30 gallon. They went to work on the GSA and diatoms, but 2 paired up and laid a ton of eggs along the back wall of my aquarium. They're not all that noticeable but the do last for a while.
I have the common green nerite (can't remember the sp.), but they have left my plants alone thus far, and love algae. I'd recommend at least 6-8 for your 55, you already have a lot of algae eaters.