1. In my 10g I had my male Betta, my 3 Otos and my Mystery Snail. My Betta recently had a run in with Fin Rot and he was put in a QT. My bottom dwellers were quite active when he was gone, but I soon noticed that my Otos were disappearing. I asked about them on another site more focused on other fish and they believed it was the ammonia levels from the snails that got them... That has been taken care of, by the way. My Betta has always been aggressive, but he has never touched the Otos. There was still one left when he went back into the 10g. Do you think that he killed the last one? I also couldn't find any bodies in the water change after he came back in. Did he eat them? I had to move the Mystery Snail out, my Betta was biting his antennae off :/ I won't be housing anything else with him, but do you think he killed off that last Oto and then disposed of the bodies?
2. I am getting a new used tank soon (it was my aunt's and is in perfect condition) and it could range from 5 gallons and up. I was thinking it would be around 15 or 20 gallons, I don't know yet- is that good for a sorority? I have read the sorority thread on this page, but I just wanted reinforcements on what the number of girls I could put in there would be and how heavily to plant it.
Thank you for reading this, please respond quickly!