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View Full Version : When are T5's equal to MH in relationship to the depth of the tank?


Ixthys
01/30/2006, 09:40 AM
I've read quite a few posts of people talking about converting their MH setups to T5. Replies are typically, "if you use X number of T5's, that should equal your current MH setup.."

Clearly (at least to me!) there is a relationship to the Wattage of MH and the depth of penetration; not just the spread of coverage. Does this hold for T5's as well? What is the cutoff? How much does 'overdriving' a bulb help with depth?

Thanks!

Entropy
01/30/2006, 09:57 AM
I honesty think there are way to many variables to give you a close to accurate answer. Light penetration is going to be very specific to the setup your are running. Ballast, bulb wattage, bulb color, wiring, reflector, water clarity, and probably some things I am forgetting are all going to play a role in how much light you get to a certain depth in the tank.

werew
01/30/2006, 11:12 AM
My tank's 24" tall, a 65gallon Megaflow. With just ONE Blueplus T5HO tube, it totally penetrated the depth of my tank and THEN SOME.

Out of curiousity I took my T5HO retro over to my friends to test it out on his tank, a 150gallon +30" tall tank. Using ONE blueplus 39watt T5HO tube (using icecap SLR reflectors & Triad ballast), it lit up 75% of his tank front to back, and definitely reached down to his sandbed with authority.

Lifting the tube about 6" off the top of that tank to find out where this T5HO would start showing weakness, 6" was it. Granted... that 6" was air and not water AND the glass splash guard was on the tank!

With that said, for me... T5HO BluePlus works for up to 30" deep tanks, i'll testify to that! I'd even say possibly 36" deep.

RE: T5HO vs. MH.... they're 2 different beasts altogether...
I noticed with my 10k MH's, i'm not sure if it's the color or the point source type of lighting, but it gives my tank a crisp & clean look. This is why i chose to go with T5HO as supplemental lighting to MH's.

dvanacker
01/30/2006, 05:13 PM
Apples and Oranges.....

Ixthys
01/31/2006, 06:19 AM
Appreciate your replies...

It's all photons and energy ultimately, right? If you're comparing 6 of the 54W 10K T5s with a 250W 10K MH at any one spot on the same tank with otherwise same parameters, what's the difference?

orlenz
01/31/2006, 07:03 AM
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With that said, for me... T5HO BluePlus works for up to 30" deep tanks, i'll testify to that! I'd even say possibly 36" deep.



what readings did you get at 30" ?

fish1219
01/31/2006, 08:13 AM
The below analysis was done by the GRIMREEFER.
*******************************************
T5 ballasts compared
So I finally got some regular T5's (54 watt 4 foot lamps) to play with. I did PAR measurments 18.5" below the surface at the sandbed. The lamps were about 2" above the water for the test. The lamps were D&D, 2 Aquablues and 2 Actinic Pluses ran in Ice Cap reflectors. Tested with Apogee Quatum meter, Amps tested with Craftsman True RMS meter.

Workhorse 7: 1.5 amp draw, PAR reading 126

DYnamic T5 ballast: 1.4 amp draw, PAR reading 135
(spec T5 ballast)

Ice Cap 660: 4.1 amp draw, PAR reading 183

My 6x80 watt T5 system was 145 with an amp draw of just under 6. Seems to back up my theory that the shorter T5 lamps are way brighter when overdriven.

3x250 watt DE halides. 14K lamps on good e-ballasts about 7" higher, 6 amp draw, PAR reading 95. And people wonder why I am going back to the fluorescents
*************************************************
I was running 3-VHO's (95watts) over my 45Gallon tank (24" deep). I have swithced to 2-T5HOs (54watts). My T5HOs are running on the DY(namic) ballast. This is a new ballast being offered by ICECAP. It is available at reefgeek.com. It does not overdrive the bulbs like an ICECAP 430/660. To get the most out of T5 lighting you need the SLRs (Single Lamp Reflectors). ICECAP makes some of the best SLRs on the market.

Therbligs
01/31/2006, 09:16 AM
3x250 watt DE halides. 14K lamps on good e-ballasts about 7" higher, 6 amp draw, PAR reading 95. And people wonder why I am going back to the fluorescents

What is the reading at the same distance off the water? You increased the distance by 4.5x (9"/2", which reduces the PAR y^x. This is apples to oranges. If you are going to take measurements for the MH's at 9" (2" + 7"), you should take all of your readings with the light source 9" from the water.

Horace
01/31/2006, 09:34 AM
<a href=showthread.php?s=&postid=6631369#post6631369 target=_blank>Originally posted</a> by Therbligs
What is the reading at the same distance off the water? You increased the distance by 4.5x (9"/2", which reduces the PAR y^x. This is apples to oranges. If you are going to take measurements for the MH's at 9" (2" + 7"), you should take all of your readings with the light source 9" from the water.


For this reason exactly comparing T5 to MH is hard to do. Noone runs T5 9" above the tank because T5 run much cooler and thus allow you to run them closer than MH. But I do think his test was a REAL LIFE test because MH is almost always ran atleast 9" or higher, so it is a fair comparison. If you put T5 at 9" it would take away one of T5's biggest advantages. To properly compare them you should run them at what height they would normally be run at.

Also read closely, it was The Grim Reefer who did the experiment, not the guy who just posted the results.

Ixthys
01/31/2006, 10:41 AM
You both bring up good points. From a scientific standpoint, the bulbs should be tested at the same height off the water so that we are comparing apples to apples. But, you make a good point that it is more difficult (though not impossible) to run the MHs as low as T5s.

Therbligs
01/31/2006, 10:42 AM
I'm running 4.5" from the water line DE MH's. This is an advantage of DE in that you do not have to be so far from the waterline. That's why when it comes to real life, DE will come to the top.

I was talking in "Royal" terms as to the person performing the test.

dvanacker
01/31/2006, 05:19 PM
Either way it is gonna be close.......so DE SE OR T5. They are ALL good options.

I hate people who have to boost their lighting systems none stop....its not like rooting for a profesional sports team guys.

This is lighting and their will always be more then one way to skin a cat....

dhoch
01/31/2006, 06:05 PM
Here is what I know on the subject.

T5's are better if you are looking for a linear light source.

MH's are better if you are looking for a point light source.

With T5's there will be less shady spots in the tank (making it harder on low light corals) than with MH.

In terms of what gives out more photosynthetic light. At WAMAS we have been doing a bunch of readings and have basically found (and this is kind of on average i.e. it varies from system to system depending on age of bulb, reflectors used, and ballasts used) that 250 MH systems offer a little less par than T5's (with good reflectors) do (measuring directly under the MH bulb).

After that it depends on size of tank and how much coverage you want. (plus things like cannopy design, cooling, etc).

Dave

Horace
01/31/2006, 06:10 PM
<a href=showthread.php?s=&postid=6635501#post6635501 target=_blank>Originally posted</a> by dhoch
Here is what I know on the subject.

T5's are better if you are looking for a linear light source.

MH's are better if you are looking for a point light source.

With T5's there will be less shady spots in the tank (making it harder on low light corals) than with MH.

In terms of what gives out more photosynthetic light. At WAMAS we have been doing a bunch of readings and have basically found (and this is kind of on average i.e. it varies from system to system depending on age of bulb, reflectors used, and ballasts used) that 250 MH systems offer a little less par than T5's (with good reflectors) do (measuring directly under the MH bulb).

After that it depends on size of tank and how much coverage you want. (plus things like cannopy design, cooling, etc).

Dave

Which is exactly why many pure SPS tanks are going with T5 instead of MH. Like ive said many times before. T5 is not for everyone, but it is a damn good alternative if not superior to MH for pure SPS in many situations.