T5 PAR question

[MartinM]

I’ve only ever used T5 as supplemental to MH, but now I’m interested in using them exclusively on a frag tag. The tank is 120x60x38cm (~4’x2’x14”) with a water depth of about 30cm (12”), and I want to get ~60 PAR at that depth evenly throughout the footprint of the tank. I want to mount the lights about 60cm (24”) above the tank. How many bulbs, approximately, would I need to achieve this? Guesstimates are fine, I’m just wondering if I should order a 4, 6, or 8 bulb fixture and then play around with the bulb quantity a bit from there. Thank you all!

 

[spsick]

I’ve only ever used T5 as supplemental to MH, but now I’m interested in using them exclusively on a frag tag. The tank is 120x60x38cm (~4’x2’x14”) with a water depth of about 30cm (12”), and I want to get ~60 PAR at that depth evenly throughout the footprint of the tank. I want to mount the lights about 60cm (24”) above the water. How many bulbs, approximately, would I need to achieve this? Guesstimates are fine, I’m just wondering if I should order a 4, 6, or 8 bulb fixture and then play around with the bulb quantity a bit from there. Thank you all!

You’ll lose A LOT of par mounting T5 that high.

What type of fixture and what bulbs will need to be known to even come close to guessing.

ATI fixture with Blue Plus, Coral Plus, or 6500k? Probably 4 bulbs.

 

[MartinM]

I know I’ll lose a lot but it’s more convenient to mount high for working space. PUR (and PAR, if measured by a modern meter which
I have) won’t differ significantly with bulb choice. I just want to make sure I can get 60 or so to the bottom.

I’d be using an ATI or Giesemann fixture. I might opt for 6 bulb to have options if you think 4 would do the trick.

 

[DeniseAndy]

On my 40b I have 4x39w bulbs, on my 20L I have 4x24" bulbs and have clams high in the water (bulbs about 10" off water). I would do the 39w as they cover nicely and start with 4 bulb. This will give you areas of high par and low par like 60 on the edges.

 

[MartinM]

Good point - I don’t want high
PAR. The peer-reviewed literature on the species I’m propagating pegs 60 par as most efficient. So I’m looking for the most even coverage of 60 par possible. Higher than 100 is growth inhibiting, actually.

so maybe an 8 bulb fixture with enough bulbs to hit 60 and enough room to space them out for even coverage?

 

[spsick]

I know I’ll lose a lot but it’s more convenient to mount high for working space. PUR (and PAR, if measured by a modern meter which
I have) won’t differ significantly with bulb choice. I just want to make sure I can get 60 or so to the bottom.

I’d be using an ATI or Giesemann fixture. I might opt for 6 bulb to have options if you think 4 would do the trick.

Six will definitely give you flexibility To achieve your goal

 

[oreo54]

Quantitative Comparison of Lighting Technologies: Metal Halide, T5 Fluorescent and LED

Based on this quantitative data, is its quite obvious that the LEDs have come of age in providing a viable solution to lighting reef aquaria.

reefs.com

Red square is your tank. These should be "free air" measurements sooo at 24" that is the par pattern when it hits the tank.
6 tube 36" t5ho
30" should give you some idea of the par at 36"
4 tubes "look" to be enough though 6 tubes (w/ 2 possibly removed) would be better considering this uses one of the best reflectors.

This shows 3 tube ATI would hit your par number
Note the worse the build the worse the delivery (sort of obvious):

YMMV...