MH-T5 vs LED-T5 for 4' x 3' area

[sfdan]

So I'm setting up a new tank that is 8' long x 3' wide x 26" deep. The top has 2 open sections with a cross brace in between, so in actuality I'm just going to be lighting two 4' long x 3' wide sections. To simplify everything I'm just going to talk about the lighting options for half the tank and then multiply by 2 at the end.

The tank is going to be an entirely SPS reef. My current tank is 4' x 2' and has 2x250w MHs + 4 54w T5s. I'm very familiar with this type of setup and it has had great results, but there are many aspects of LEDs that are tempting to me.

So basically, I'm going to put a potential plan using MHs and then one using LEDs.

I don't know much about LEDs, so just let me know how the LED plan compares to the MH plan and feel free to offer any feedback you think might be useful. Is this enough power? Is this good placement?

In both graphics I've shaded where the bracing is.

MH-T5

2-250w MHs with 16x16" reflectors, with 4 T5s running along both sides.

Wattage: 2 * 250 MH + 216 T5s = 716 * 2 = 1432w

LED-T5

Whether I go with Kessils or XR15s, the configuration would probably look like this with 4 LEDs and 6 T5s (the XR15s are a little bigger but the general gist would be the same).

Kessil wattage: 4 * 90 + 324 T5s = 684 * 2 = 1368w
Radion Wattage: 4 * 95 + 324 T5s = 704 * 2 = 1408w

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I was surprised when doing this exercise that the LEDs really don't save much wattage (of course I put an extra set of T5s in there), but I'm very tempted by the adjustability and lack of having to replace the bulbs.

However if I need to start adding extra LED lights/pucks to actually equal the MH setup that might help tip my opinion one way or the other.

 

[HaroldT]

For that size tank and since you are doing entirely SPS - go with metal halides. You have them now so you can just use what you have to save money.

Plus - after using LEDs and switching back to metal halides, I find SPS growth to be a lot better under halides than they were under LEDs. Also more even growth patterns and no problems with shadowing to worry about.

 

[jda]

I would suggest the MH as well - reflectors are your friend on big tanks. I think that you will need 4 30s over that area to truly replace a pair of 250W MH, or at least 6 15s. Kessils are a joke for coverage and output, IMO - others will disagree.

In any case, I highly recommend that you get and take advice from SPS folks who have lit a large tank like this. Lots of people mean well and think that what they do over their cube or smaller tank will scale, but they do not... large tanks have their own unique problems and solutions. Dr. Johsi's tank is a good example, which has plenty of info readibly available online - 10 Gen 4 30s to replace 3 MH and he does not use T5s.

I am ordered, planning and accumulating stuff for a 144x42x30 tank and it will be MH only - no T5s. I will probably use 6 250s and 2 400s MH. I know the difference in performance (which is substantial), but this also is as cheap as I can buy the equipment and run it. I am in Colorado, so IR heat is absolutely no problem for me.

 

[jda]

Lastly (sorry for two posts), in your second example, it looks to me that this is a T5 lit tank with LED supplements.

 

[sfdan]

I would suggest the MH as well - reflectors are your friend on big tanks. I think that you will need 4 30s over that area to truly replace a pair of 250W MH, or at least 6 15s. Kessils are a joke for coverage and output, IMO - others will disagree.

In any case, I highly recommend that you get and take advice from SPS folks who have lit a large tank like this. Lots of people mean well and think that what they do over their cube or smaller tank will scale, but they do not... large tanks have their own unique problems and solutions. Dr. Johsi's tank is a good example, which has plenty of info readibly available online - 10 Gen 4 30s to replace 3 MH and he does not use T5s.

I am ordered, planning and accumulating stuff for a 144x42x30 tank and it will be MH only - no T5s. I will probably use 6 250s and 2 400s MH. I know the difference in performance (which is substantial), but this also is as cheap as I can buy the equipment and run it. I am in Colorado, so IR heat is absolutely no problem for me.

Great info, thanks. Yeah I saw the video of Sanjay's tank and was shocked by how many LED fixtures he had to have on it. That piqued my curiosity a bit for just how many LED units you actually need to match a MH. I was a little confused by his whole explanation though, in that he replaced 1200W of MH with 10 Radions that each use 190W, and yet this is somehow much cooler. Is it that LEDs just don't run at the full percentage very often?

Lastly (sorry for two posts), in your second example, it looks to me that this is a T5 lit tank with LED supplements.

In some sense, it is. I really like the look of T5s, and frankly I think the color of my tank is best when only the T5s are on. I've tried many different MH bulbs, and currently have settled on the Radium 20ks, but to me it isn't the same as with the T5s. Of course I can live with it as the corals are happy, and the corals being happy makes me happy.

This to me is the real pull of the LED system. I *know* I can get a color I like with the T5s and then the LEDs would supplement the lighting intensity while also allowing me to dial in a color that I know I'd like, plus providing the shimmer from a single point light source. But the math only works out if I can pull it off with 4 Kessils or XR15s. Any more than that and the upfront cost cannot be worth it unless I'm saving tons of power.

The thought of finding a way to potentially cram 6 T5s in with the MHs did spur a little research and if I went with a Cabo Sun Mini reflector, which is 13"x13", I would have enough space for 6 T5s with the MH. That is probably the new leading contender.

 

[jda]

His tank is interesting. He uses more power on the lights than he did - he runs them really white and high power on all channels. His heaters work more and chiller runs less - push in power with a lean to more heating. Overall, the has saved no power. The MH heat the water up a little bit with IR - it is not all dead-short type of heat, but that many panels in the hood will heat up a bit too. ...but now we are hearing that IR is important for coral growth (Dana Riddle is hinting at a new study). In a large tank, the heat can be a blessing and it is easy to plan for it with ventilation and fans the few months that it gets hot.

I don't buy into this best-of-both-worlds garbage. If you want a T5 tank, then invest in it 100% and swing away. Nearly nobody can hit for power and average (only the elite)... two quarterbacks mean that you have none... don't even get me started on a half-cheese and half-pepperoni pizza... keeping room for an inferior light instead of just going 100% with what you like the best is not great, IMO. This is why I don't run T5s - I love the look of 14K Phoenix all by themselves, so I take the extra T5 wattage and put more MH over the tank. 36" might need 10 or 12 T5 bulbs to spread, so that is a lot of bulb changes x2... but if it is what you love, then just sell a few more frags to cover it.

Copps solved a similar problem with MH. Ed uses overdriven T5s. JB uses MH too. There is a sweet tank from Europe that was about 300G that used LEDs, but covered the WHOLE TOP in AIs - like 36 of them and now regrets it. Those are good tanks to look at.