Light hood rebuild... Advice sought

[dow]

I've got a 65 g tank that I've had set up for about two years or so. Before that I had a 40 breeder (same footprint) for about three years. With the 40 breeder, I set up a light hood that housed a single 175MH lamp, which was great for the 40 breeder. The hood is designed so that the lamp is about 9" above the water and is enclosed except for a gap in the back that is 4" tall and runs the length of the hood. When I moved to the 65, I didn't make any changes to the lighting due to money issues and because I really didn't need the additional light for mushrooms, polyps and fish. However, the 65 came with glass cross brace that's about 5" wide or so, and is directly below the middle of the lamp. Here's a diagram of the original setup:

http://www.flintrockdesigns.com/images/images/hood-original.gif

Well, I recently upgraded my lighting from the single 175 to a dual 250 MH setup. I did the upgrade for a couple of reasons. 1. I'd like to move from mushrooms to stonies; 2, I'm trying to get away from having the center brace block part of my light; and 3. I got a great deal on two ARO 250w electronic ballasts (Thanks Henry!) (I already had the second mogul socket and reflector). The current setup looks like this:

http://www.flintrockdesigns.com/images/images/hood-current.gif

With the new lighting, the tank looks great. However, heat is an issue. I've added one of the larger Radio Shack 110v fans to the back and it's blowing air into the hood, which is causing air to circulate in and then back out the back, but it's not helping enough. In order to keep the tank within an acceptable temp. range, I've had to cut back to running one light at a time.

I've got a few options that I"m considering, and would like your advice and recommendations on them. I'd like to stick with the same hood (with some modifications) if possible. Here's what I've come up with so far:

1. drill some vent holes in the top to give the heat a place to go and possibly add a second fan to the back;

2. Drill a hole in the end of the hood and install the fan there, with possibly a second fan at the other end to push air through the hood;

3. Make the modifications in #2, and re arrange the lamps in this format, so that the air is running along the lamps from one end to the other:

http://www.flintrockdesigns.com/images/images/hood-proposed.gif

As much as I'd like to go with a pendant design, that isn't really practical in this case sine the ceiling is about 16 feet up here, and I don't think that my wife would bee too gung-ho on having wires hanging from the ceiling down that far.

Any thoughts or ideas that you might have would be great.

Thanks,
Dow

[erikharrison]

You can run fans across your sump as well. That is alot of light! :) Altex sells a fan that moves 110 CFM for around ten dollars. You have to solder it, but they also sell the shrink wrap for the wiring which you can seal with a lighter. I would say fans galore, but I have 0 idea at what temp your tank is running at with both MHs on. Got a number for us?

[dow]

You can run fans across your sump as well. That is alot of light! :) Altex sells a fan that moves 110 CFM for around ten dollars. You have to solder it, but they also sell the shrink wrap for the wiring which you can seal with a lighter. I would say fans galore, but I have 0 idea at what temp your tank is running at with both MHs on. Got a number for us?

With both lights running from 3:00-11:00 pm, it gets up to 85-86 in there, according to the new fancy electronic digital thermometer that I got from B&B. Obviously that's hotter than I want it, and hotter, I'm sure it's hotter than the tank critters want it.

[hobogato]

use the fan(s) to cool the water, not the lights. find a way to have the fan blow onto the surface of the water to encourage evaporation - that will help keep your tank temps down. you may also consider adding a fan over your sump (lke erik suggested) to blow on the water in the sump to add to the evaporative cooling of the tank.

[dow]

I wish I'd have know about the altex fans earlier. I gave 24.99 for the Radio Shack fan and it's rated at 65 CFM.

[KyleV]

I have the exact same tank and light set-up (plus 2 39watt T-5 atinic). I run 3 small walmart fans aimed at the surface of the water in the canopy and 1 blowing on the surface of the sump. My temp doesn't go higher than 82 with both on from 1:30 to 9:30.

[KyleV]

I was going to drill holes in the side of the canopy but tried this first and it worked.

[dow]

I have the exact same tank and light set-up (plus 2 39watt T-5 atinic). I run 3 small walmart fans aimed at the surface of the water in the canopy and 1 blowing on the surface of the sump. My temp doesn't go higher than 82 with both on from 1:30 to 9:30.

That's good to know. I went to Walmart originally, but they only have fans in the summer, unless you want to go with a 20" box fan (which would do the job, but won't exactly fit in my setup).

[erikharrison]

I have space behind my stand and I have a large oscillating fan back there. It works pretty well.... I am going to build a holder out of acrylic to hold four 120mm fans. Then I am going to link them together using the connector (4 pin molex, the standard 4 plug power connector in a pc) and at Altex they have a power plug that fits (female ended) on the red wired pin on the 4 pin connector. You slide the red pin into the power and bend the negative over to touch the outside portion (sleeve) of the power cord. The inside is positive, the outside negative. Then you just solder the pin on the outside to the power. The power cord has an end that looks like the kind that you plug into your laptop. They are much more expensive than the walmart fans, which I think are 5 dollars though!

[Bill S]

Did I read somewhere that moguls should be mounted like your middle diagram rather than the last?

[dow]

Thanks for all of the advice, guys. I picked up a couple of the 110 CFM fans from altex, and will be putting them in tomorrow evening (in the mean time, the door is staying open in the hood with the single fan running in there. It's helping, but not as much as I'd like.

Oh, by the way, those fans have gone up. They're now about 15.00 each, and you can get a plug-in cord for them as well.

[erikharrison]

Thanks for all of the advice, guys. I picked up a couple of the 110 CFM fans from altex, and will be putting them in tomorrow evening (in the mean time, the door is staying open in the hood with the single fan running in there. It's helping, but not as much as I'd like.

Oh, by the way, those fans have gone up. They're now about 15.00 each, and you can get a plug-in cord for them as well.

Those things push a TON of air. If anyone else needs them, and you can get to the Altex on 35, ask for Tom and he can solder and shrink wrap the plug in cords for you. For a fee of course!

[dow]

Those things push a TON of air. If anyone else needs them, and you can get to the Altex on 35, ask for Tom and he can solder and shrink wrap the plug in cords for you. For a fee of course!

Man, you aren't kidding about that. I mounted the fans, one in each end of the hood, both pointed in. My heating issues seem to be taken care of now. Thanks for all of the great advice.

Now I've got one more question. What can I do to cut down on the fan noise? It doesn't bother me too much, but SWMBO says it's loud, so I need to fix it.