So I've been looking to cool my 120 gal. tank and I don't want to buy an expensive cooler for it.  So I thought I would make my own cooling unit.  I already have 4 fans blowing on all my water and sump and it still doesn't cool it enough.  So here is my thought:

I will use a small pump to pump water out of my sump into either a radiator or transmission cooling system.  Then I would have 1 or 2 fans blowing on the cooling system.  As the water passes through the cooling system it would cool down the water and then release it back into my sump.

Does anyone see a problem with this?  I'd like your opinions.  Especially Mark Peterson who is the master of DYI

Radiators,  and transmission cooling radiators are made out of copper. The salt water WILL corrode them and destroy a reef tank.

Your Idea is great but I doubt you will find a titanium radiator to make it work.

My first question is: What temperature is your heater set at?

Second question: What brand of heater and is it coming on before the set temperature? Well that's really two questions, so, Fourth question: Depends on the answers to the first three.

Essentially, what I am suggesting is that the base temp is too high. The tank should be able to cool to as low as 74 at night so that during the day when the lights are on, the temp can rise to 80 without problems.

Keeping the room cool also has a great effect on tank temperature. What is the daytime room temperature?

WELCOME HereFishyFishy.

What size are the fans? I have two 250 watt MH on my 120 gallon and keep it cool with one 7" fan. I think we can help you do this without too much trouble or expense.

Mike

Hey I have been thinking about this issue for my system as well and I choke when I see the cost of chillers. I am in the HVAC business and have been for some time and it just looks crazy to me to see these itsy bitsy cooling systems cost as much as the equipment for an entire house.

So with appologies to Mike (because I really do agree with the keep it simple approach) here is what I am considering . . .

I have a small refrigerator that I no longer use. The compressor on it is rated at around 1/5 HP as I recall, which as far as energy used equates to a decent size commercial tank chiller. (I need to verify this and the BTUH rating for better comparison)

I was planning to coil as much PEX piping (1/2" dia) as I could inside the cooling compartment and possibly place it inside a bucket full of water to act as a better thermal mass. After drilling two holes in the side of the refrigerator I would extend the piping to my sump and place an inline pump at the head of the piping.

Control could be a simple aquastat that would close a contact relay to start the pump on a call for cooling. The flow will want to be fairly low to permit the release of heat in the refrigerator compartment and to minimze the stratification in the sump. I realize the unit may not be able to keep up with the demand at all times but due to the mass of the tank and the potential in the mass at the cooler it has a good chance of working. 

I will be doing some more research on this in the coming months and will happily share my findings for any interested.

I know it's kind of a an unsystematic approach and I may be a bit irresponsible for mentioning it without more research but, there I've said it.

YMMV

Rod

Here is my setup:

120 galon tank

Two 250watt 14k hamilton MH (10" from the surface of the water)

Iwaki external pump

Four 6" fans (don't know the evaporation rate because it is all automated with automatic RO top off water)

I don't use my heater.  Night time temp is about 74deg.  and about 84deg. when the lights turn on.

The tank is in my basement so the room temperature usually stays pretty cool

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Now with that being said, I found a transmission radiator that was made out of aluminum.  So HoldenCraft's concern about corroded copper may not come into play.  Is aluminum ok for a salt water tank?  Perhaps I'm reading into this too much, but is 84deg too warm for a tank?

Fishy,

Yes 84 is too warm especially this time of year as it will probably increase when the weather heats up.

My lights are also 10" from the water to the bulb and my pump is in the sump so it adds heat too. Aluminum also corodes in salt water.

Something sounds fishy here.

If the tank is in the basement and it still rises 10 degrees something is not behavein as it should or you have it set up different. Can you describe how the lights and fans are situated.

It sounds very familiar. Did you post about this under another name a while back when you were building the hood and putting in the fans?

There are many variable that could cause this tank to be warmer than someone elses tank that runs more and hotter lighting.  I'm afraid I may soon be dealing with the same problem.  I now have 4 tanks in the room I call my office in the basement.  The lighting puts off enough heat that in the afternoon I have to open the window to let cool air in even in the winter.  (and to think I used to freeze while trying to work in here in the winter.)  I'm not sure what the answer is, but I'm sure I'll be looking for them soon myself.

Here is an interesting question I've been worried about as things warm up that also has some tie to this thread:  For those of us that cool our homes with Evaporaive Swamp Coolers  has anyone noticed that they have enough humidity in their house from tank evaporation that the Swamp Cooler doesn't seem to cool like you might think it should?

Are you serious? 74-84 every day. That swing is crazy let alone that your 84 during the day every day. 

I have a 125 with 4-4' vho and 3-175mh 8" off of the water. I have 2-4"fans sucking the heat from the halides out through the top of the hood. After I put egg crate over the water I added a 4" fan blowing over the tank water. It is in my basement and the tank temp goes from 77 at night to 79 during the day. I do run a heater.

You must have a totaly enclosed hood to heat it up that much.  I would recomend you figure out what is wrong fast. Your too hot and have too far a temp swing. 4-6" fans should keep that tank very cool if the heat has somewhere to go. As Mike said aluminum will corrode and contanimate your tank.

Please post some pictures so we can be of some help.

Will, Ive noticed that my swamp cooler does not seem to work like it used to before I went tank crazy. Question for you...Do you get sunburned with all of that light in one room?

I forgot to mention that I run two blue 4' VHO's as well.  This is how I setup my tank:

I run 2 fans 24/7.  About 11a.m. my two blue VHO's kick on.  Around 12 noon my 2 MH kick on along with my 2 other fans.  Around 10p.m. my MH turn off along with the 2 extra fans.  About 11p.m. my 2 blue VHO's turn off.  So my photo period is approximately 12 hours.

The comment from Gahlenfr is making me think.  I might be pushing hot air around.  I have one fan 24/7 blowing on my sump (no cold air coming in).  I have all other 3 fans blowing down from the top of my hood.  Yes, I have an open hood so all my fans blow down onto the water.  However, the top of my hood is only about 6" from dropped ceiling.  So I don't have a lot of clearance.  Could that be my problem?

Okay, I see the problem. What you are starting to think is right. But there is more.

Remember that hot air rises above cooler air. The fans are pushing hot air from the ceiling down past the hot lights and with all the lights in the path, the heated air probably doesn't hit the water directly. This is why there is practically no cooling effect.

Flipping the three fans around so that they suck instead of blow will cool a little better, but that option would not make best use of the fans cooling power and it corrodes fans to pull humid salty air past them.

Here are some other options that will do the job.

-- Drill holes and mount a fan on each side of the hood, blowing in.

-- Mount a fan on each side of the hood in the back opening and place it on a bracket so that it's aimed diagonally down across the surface of the water.

The second option is the most effective way to cool the tank. Both options eliminate your two 24 hour fans altogether (the sump fan is definitely useless). With three holes already cut in the top of the hood, there will be ample avenues for hot air to exit and the cooling/evaporative effect of pushing cooler air over the water surface will do such a good job that I'm guessing the fans can be set on the same timer as the MH's.

After the change, please come back and tell us how much better the tank is looking with the temperature at 80 and below.

That's much, much better. Are you willing to work on it a little more to get it down to 78 max? If so, please fill in some missing info.

Are the fans running 24/7 or just when the MH's are one?

Are the two fans taking air from outside the canopy?

Can you give us a measure of the angle at which the air from the fans is hitting the water? and how much are they angled in to the canopy area?

What is the actual room temperature?

And last, would you be willing to reduce the MH Photoperiod by 2-4 hours?

Sorry for all the questions, but this info really does make a difference.

I have one fan at the top of my hood pushing the hot air away 24/7.  It is setup on the far left side of the hood so it can draw in cool air from the room temperature and blow it across the top of my hood to the other side.

I have one fan running 24/7 directly on the water surface.  The other fan that I have running directly on the water surface only kicks on when my MH turn on.  These two fans are hitting the water at a 45 deg angle because that was the steepest grade I could get with the room I have to work with.

The actual room temperature usually runs about 72deg.

I don't have a problem with reducing my HM photo period.  I just figured the more the light the better growth from my corals.  No??