Ok so 2 of my tropical tanks have heaters, they stay between 78-81 depending wat I set them at..now my 10 gallon without a heater stays at 82 degrees which is warmer than the ones with the heater, same with 1 of my gallons, and then the other 5 gallon stays at 78 degrees. And my goldie tanks used to stay perfectly at 74-76 degrees (although they're at 78 now). Why r they higher in the non heated tanks? (both 10 gallons have incandescent bulbs, 20, 5, 5 have flourescent)

One of the factors might because of incandescent light. It generates more heat than florescent.

yeah but then again..i've got 1 10 gallon with incandescent bulbs and a heater..it stays at 77 degrees. The other 10 gallon also has incandescent bulbs and no heater and it stays at 82 degrees

I agree that the incandescent bulbs may be heating the water. Also, consider the location of the tanks in the house: sunlight and a warm room could warm the tanks, or cold air coming off of a window (even if it's closed) could cool a tank. And, finally, a thermometer might not be perfectly accurate, so if you are using separate thermometers on each tank, perhaps they are not all calibrated the same.

I was going to mention everything that A Penguin just did, but he got there first!

Are the tanks with different temperatures the ones on the stands? My only other thought is about the power strip I can see under the stand. If the one on the bottom is getting hot, it could be the power strip. Some of those converter plugs put out a lot of heat.

yeah they are the ones on the stands. I could check later if the power strip thingie is giving off any heat but its closer to the cooler heated tank. But then again ur right, they do have different thermometers, im gonnna try taking the temps with the same one later