First tank was at 15. Had four tanks in the last 20 years. I don't have a green thumb for keeping fish alive. I have changed to cold water feeder fish due to this. My favorite fish are the swords, red tail shark and Plecos. My current set up is 65 gallon with 9 feeders that been in tank year and half. Got 12 of them at once 3 sadly didn't make it. Three months added Plecos about 2 inches, worries about him. He is great, cleaned my tank within a week. Added 3 groupies from a friend's overpopulated tank (they won't stop breading) a month ago. Ph 7.6, temp 68 to 72f, no traces of NH3/NH4+ or NO2, 40 PPM of NO3. My main purpose her is the Plecos concern.