Join Date: Feb 2008
Location: Garden City, NY
DIY Low profile light hood for 120g tank
So about a month ago my son and I bought a used 120g tank off of Craigs list. It came with a stand, an Ehein ProII Canister filter and a light hood that had 4 X 36" T8's at 30W each. It was cheap and we were looking for a DIY planted tank project. The hood did not put out enough for a planted tank, so we decided to build our own low profile hood.
The materials list included the following:
2 - 8'x1"x4" pine boards - $7
1 - 4'x8'x3/4" cabinet finished plywood -$27
3 - 4 bulb (32Watt max each bulb) electronic ballasts of of eBay - $25
26 - "humidity resistant" Fluorescent tube, double pin, sockets - $32.50
1 - Spool 14 gage copper wire - $14.50
1 - GFCI 5 way outlet - $28.00
1 - 48" LED tube 5000K and 1050L 14watt (Moon Light on 1 zone) - eBay $26.00
2 - Double switch boxes & plates - $6
4 - SPST switches for 4 zones- $9
8 - 36" T8 bulbs 3000-8000k on 3 zones (already had 4 from the old fixture)- $64
plus assorted screws, wire nuts, paint, zip ties, etc -$40
The completed light box is 73.25" long by 12.5" wide and 3.5" high and covers the back 3/4 of the tank. I used teflon coated deck screws to build out the box and they are all counter sunk with a waterproof, wood putty overlay, then sanded to a smooth finish, with 4 coats of black enamel over the exterior of the box. The interior has 3 coats of bright white water resistant enamel.
On the interior, we used brass mounting screws on the humidity resistant sockets, out of concern for rust that might occur with steel screws.
The tricky part was wiring 13 bulbs to 4 switched zones through 3 electronic ballasts. Each ballast controls 4 bulbs. The LED is wired directly to 120v and does not need a ballast. We are talking about LOTS of wire.
If you try to build one of these, get some masking tape and number your ballasts and the associated wires coming off of each ballast. It's easy to do if you follow the wiring diagram on the ballasts and keep everything in order.
Also, give your ballasts plenty of air. Don't pack them next to each other. They get warm and need to breath. Each ballast has 4 screw mounts. To give a bit more air behind the ballast, use a washer under each mount to lift the back of the ballast away from the wood. In my tests, the ballast that I'm using are just warm to the touch, after several hours, so this may not really be a necessary precaution. All of the ballasts, switches and wires run along the outside along the back of the hood, out of view, so the front, top and sides have a very clean, low profile.
If you like, there are digital timers, that are the same size as the large switches that I used for this project. They are a bit pricey, so for now, I'm going to stick to the manual switching. The first one I will replace with a timer will be the switch for the LED moonlight. With all 4 zones on timers I can probably replicate just about any lighting situation, from sunset to moonrise....
Attached are some images. Note that 4 bulbs are missing for zone #2, but you can see how bright the 48" LED strip is on the left. I was really surprised by this and we may end up putting a blue tinted sleeve over the LED's
Overall it was a fun project. The new unit can put out up to 384 watts (not including the LED) but the ballasts give me a range from 25 to 32 watts per T8 bulb, so I'm going to try and keep it in the 2.5 wpg range since we are working towards a low tech tank, but we still have the flexibility to put out more power if we want to in the future.
Happy to answer any questions.....