Im egar to get a rtc and im saving for a custom made tank but was wondering how long a 120 gal would last one from about 3-4 inch the measurments are 5 ft long and 2 ft wide. I was thinking about year to year and half what you guys think, id like to say I know quite abit about the rtc so dont need to be reminded on there size tank mates etc. It would be a SA rtc just want to know how long you guys think. From what ive reasearched its about a inch to even 2 inch a month please correct if wrong.