Is there anyplace to get a quick basic rundown of exactly what one needs to build an LED Fixture?
Nope. :lol:
It's pretty straightforward though. You need:
1) LEDs themselves. Cree XR-E Q5 cool white and blue or royal blue, somewhere near a 50/50 mix. If you can get the new XP-G LEDs for the cool whites, all the better. Or, Luxeon Rebels are almost as good, but have a slightly wider field of view. Don't use any other LEDs without understanding the implications of efficiency, etc.
2) Something to bolt them to. Typically, people are using MASSIVE extruded heatsinks. Unless you have a very high density, a very high drive current, and little or no airflow, it's probably overkill.
3) Something to cool them. See #2, plus a PC fan per every foot of tank (I'm making this up!) to provide air movement.
4) Something to drive them. The easiest thing to do is get an off-the-shelf constant current driver at an appropriate drive current (buckpucks or meanwells are the most popular). If you use a driver that requires a 120v AC power source, you can plug it into your wall. If you use one that requires a DC source, you'll need a DC power supply.
Once you've chosen components, you need to do some math:
First, determine an overall intensity you want. This will help you pick LED count and drive current. Most people are driving at 700mA or 1000mA, IMHO this is borderline too high for these rigs, unless you have a tall tank, and/or are using pretty wide spacing. My preference would be for 500mA for short tanks or 700mA for tall tanks. For spacing, figure 10 - 20 square inches per LED. Near the 10 range for more intensity or a deeper tank. For a 6 x 2 foot tank (your 180), this means 100 - 170 LEDs, roughly. In your case, replacing 250w MH, I'd probably go with ~140 and drive them at 700mA, with a dimmable driver so I could turn them down if they were too intense. Or maybe just a 500mA driver.
Now, you can start to estimate cost. Most of these fixtures are costing people around $8 - $10 per LED (probably a little less than that if you're careful, but we're trying to be conservative here.) So if you did 140 LEDs, you can plan on $1200 - $1400 or so.
That sounds like a crapload of money I'm sure, but consider that you'll have NO lamp replacement costs (at least for 10 years - and at that point you can just drive them a little higher to get the lost intensity back). Also, this fixture will use around 250w of power, and will be replacing your three 250w MH (which probably burn around 800 - 900w: most 250w ballasts consume more than 250w.) So, you're saving ~600w of power. If your lights are on 10 hours a day, that's 6kWh per day. If power costs 15 cents per kWh, that's around $30/month.
If you figure you're replacing those three MH lamps once a year and they cost $75 each, that's $225/year savings on lamps, and $360/year savings on electricity. $585/year savings total. So the LED fixture will have
paid for itself in just over two years. After that point, it's all gravy. If you figure your tank will run for 10 years, the total cost for the LED system will be around
$4,600 LESS than the MH system.
What would you recommend for just actinic supplementation for my tank?
Some fraction of the above, but with all blue or royal blue LEDs. If you want to try and guess an "equivalent" supplementation compared to what you'd try to do for T5 or PC, pretend like the LEDs will need ~40% the wattage. So if you would typically put 100w of T5 on the tank for supplementation, build an LED fixture with 40w of LED. If you drive at 700mA, that's probably around 15 LEDs. It'll be hard to space 15 LEDs evenly on a 6' tank, so you might want to plan for 20 or 30 and drive them lower (500mA or even 350mA.)
