Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
I have run many tanks for many years with no UV sterilizer. I have 2 on hand, basically small and large for whatever tank might need them, but have rarely used them.
They are useful when something like Ich or other problem shows up, but that mostly shows in my quarantine tank. (usually 10 gallon) A small UV for that tank is quick and easy to set up, run as needed, then turn off. No need to run one full time, and I do not want to anyway. Any diseases new fish are bringing in I want to see and know about. I do not want them suppressed while the fish are in quarantine, only to show up in the main tank.
I have run one in a larger tank, temporarily, but I do not remember what I was treating for, that was several years ago.
So, the short answer is: No, you do not need to keep a UV sterilizer running all the time. Nice to have one in case of emergency, but I would not buy a self-cleaning one for such rare use.