mine was running at around 160 for a year... i was doing an experiment about "Old-Tank-Syndrome" and in the year i didnt do a water change or clean the tank at all... all my fish (small community) survived... i even added other store bought fish and added them straight into the tank with no noticable problems. But thats over now as i felt bad for the fish and that tank is usually sitting between 10-20 with live plants and every other day 25% water changes. (its also way overstocked)