I have two gulpers in a 55g, and i found a great deal on a 7 inche arrow. He was longer than the gulpers so I thought Id put him in with them until I could build a more secure top my 90g, because the 55 had glass and i know they jump hard. the 90 only has a screen over it and i didnt know if he could get through. so i left him in there and everything seemed fine. occasionally the gulpers would bite on him, but it just seemed like they were trying to scare him. they also had full stomachs. anyways i went to the market for 30 minutes, and when i got back, wouldnt you know it, the aro was gone and one of my gulpers was twice as big. i dont even buy $45 meals for myself, nevermind the gulper