Heater OVERLOAD!! Tank @ 86!!!

Question
My new heater went haywire!!  I set it at 78 when I put it into my tank tonight, and I just went into the living room to check on my Mollie fry before going to sleep and noticed that the water seemed very warm.....so I check the thermometer and it said it was 86 degrees in the tank!!  So far all the fish are still alive, but what do i do to bring the temp down without putting the tank into shock and killing my entire community???

I have a 30 gal tank with 3 mollies, 5-1 day old mollie fry , 5 tiger barbs, a clown loach and 4 cherry barbs.  Mostly worried about my adult fish...two of my Mollies are pregnant, and my clown loach is just a baby!  Everyone is swimming around the tank even though the lights are out.

Please help!!  The heater was suppose to be better than the old one that broke last night, it has a temp dial instead of -/+.  So I thought when I set it to 78 I would be safe.  But this is ridiculous!!  I bought 2 of them and put one in my Blood Parrot's tank, but her temp is only at 80 (a little higher than I like, but I can bring her down 2 degrees easier than the 8 degrees te other tank is overheated to)

Answer
Hi Marcie

The only thing you can do at that point is to unplug the heater and let the tank temp drop on it's own. Don't worry, it shouldn't drop more than 2 degrees per hour.

Another thing to point out is that the heater should be in the center of the tank, and your thermometer on either side against the side glass panel. This will give you a more accurate temperature reading.

When it comes to aquarium heaters, they are not all the same, nor are they always accurate. You should start on the low side then gradually raise the temp until it reaches your desired temperature.

Hope this helps, good luck!

Richard