MH REALLY add that much heat :(

[banditpowdercoat]

Well, even though its cooling off, my talk still gets warm. I have a 6" clip on fan blowing across tank, its set up to come on/off with the lights. But, after lights and fan go out, I am noticing the temp still climbs. Up to 83 in morning. House temp cools down to 68-70 over night. Does the MH add THAT much heat to the rocks that it keeps heating tank after lights out? Leaving fan on 24/7 I get ALOT of evap. I have 2 external pumps, Ampmaster 3000 and Little Giant 4mqdx as well as a Mag 7 submersed running the skimmer. Heaters have been unpluged to eliminate problem there. Lights are 2 150w de and 1 250w se 10 hrs for de, 7 hrs for se light

[fkshiu]

All three of those big pumps running 24/7 really add a ton of heat, the Mag especially. Try running skimmerless to see what happens.

I ran a little Mag3 on a Remora skimmer in my old 46 gallon and I ran into cooling issues all the time with nothing more than a 4 x 39W teklight over the tank.

[christyf5]

Try running the fan to stay on for awhile after the lights go off, I found it really helped when I was running my tank without a chiller. I also had a fan in the sump running 24/7.

Also if you can aim the fan across the water just under the lights (but not directly at the lights), that might help in the amount of heat hitting the water.

[banditpowdercoat]

Ya, I changed the moonlight timer, to come on with the 150w's, (11am), then off at 3am, I put the fan on with the moonlights. No worry fro moon lights being on LOL.

I have a couple computer fans in the sump. And the external pumps add heat to the water too? I know they make the sump cabinet a bit warm, but they really add that much? ya I need my skimmer LOL. even as crappy as it is. Mag's add alot of heat do they? Guess I should work on converting this berlin Turbo skimmer to recirc, to use a smaller pump? Save some heat there?

[PoonTang]

If your tank is 83 in the morning ? before the lights come on? then your problem is definately your pumps. Does the tank cool down once the fans and lights come on? You will either have to run the fans 24/7 or hook them up to a controller or get better pumps.

[banditpowdercoat]

What I'm asking is how can an external pump add heat to the water?? And what BETTER pumps? thought my pumps were not that bad? other than the mag.

[mseepman]

Some external pumps use the water they pump for cooling and therefore transfer their heat to the water in your display.

If your heat is still there after the lights have gone out, then it's for sure you pumps. I know the Mag's are big heat makers so that might be your main culprit.

[banditpowdercoat]

Some external pumps use the water they pump for cooling and therefore transfer their heat to the water in your display.

If your heat is still there after the lights have gone out, then it's for sure you pumps. I know the Mag's are big heat makers so that might be your main culprit.

Ohh, if they use water for cooling, t hat I can see, but my 2 externals don't use water for cooling. The mag, yes, its submersed. only 43w though, wouldnt have thought that would be enough, but maybe huh.

[fkshiu]

Ohh, if they use water for cooling, t hat I can see, but my 2 externals don't use water for cooling. The mag, yes, its submersed. only 43w though, wouldnt have thought that would be enough, but maybe huh.

Water still forms a jacket around the impellers of the external pumps thereby transferring heat. Not as much as an internal pump, but there is still heat transfer.

Mags are infamous for being heat generators.

[pterfloth]

I run 3x400w on my 200 gal tank. I use two small fans blowing across the top of the tank for cooling. When the lights are off, the tank cools quickly overnight, so much so that the heater kicks in to maintain temp.

It sure sounds like your pumps.

[hillegom]

I think it would also help if you get rid of the heat in the cabinet. For sure that heat will warm your sump and then to the DT

[Aquattro]

For the question, do the rocks retain heat and add it back to the water after the lights go out? No. Once the lights go out, temp should drop again.
For pumps, my MAG 12 is the only thing I use to heat my 20g makeup water tank, it keeps the water at 81. Pretty much any pump will transfer heat, some more than others, submersibles transferring the most.
Fans pointed across the surface will help a lot, but will evaporate a lot of water. This is called evaporative cooling and just for that reason :)
The most stable method to keep temp set is a chiller. That being said, if you only swing a few degrees each day, it's probably not a concern.