T5 questions from a T5 noob - help please

[Mark_C]

So, I’m running an IM 30 AIO, 36” long. Tank is 12” deep.
Decided to do the T5 thing on this tank, so 4” above the tank is a 4 bulb T5 (36”/39w bulbs).
Bulb brands are mixed now, Geissman and ATI (2 blue, 1 actinic, 1 coral plus).
Two lights run from 10am to 6pm, with additional 2 kicking in from 12 to 4pm.

Some of my montis are losing color in patches, and now a few sps are showing the same. One or two are growing very well.
I have no idea if I’m beginning to kill corals from too much par, too little par, too much light time, or too little light time.

So, a few questions from a new T5 guy.
For such a popular lighting method there’s remarkably little ‘layman’s’ information about.

1. Is there a ‘general PAR’ reading for a generic 4 bulb setup at different depths? I understand each bulb is different, but assuming a quality bulb, is there an estimated 'somewhere in the ballpark' par at 0”, 6”, 12”, etc?

2. In a 12” deep tank, lights 4” off surface, in general are 2 T5s enough light? Are 4 T5s too much?

3. Tied in with the above question, I’m running 2 bulbs for 8 hours. During this there is a 4 hour Period with 4 bulbs on. Is this too little? Too much?

 

[WIReefer]

Really just depends on the type of corals you which to have 4 inches might be a little to low I have my 6 bulb fixture hanging 9 inches above water. Best way to find out is rent a par meter.

 

[Tiki Reef Joshua]

I had the same tank. I’d be concearned with the width of the tank and fixture. Width as in front to back. You don’t want tons of light in that back sump part.

 

[Mark_C]

With the supplied mounting legs for the T5 unit, it puts them 4" over the tank, there's minimal light spill into the back compartment (and it only hits black plastic, not the waterline)

 

[Tiki Reef Joshua]

I think getting the par meter is a good idea.

 

[nereefpat]

I have T5s, and I love them and recommend them. Any combo of those 2 brands of bulbs should be plug and play, and you should be able to grow corals well. That being said, I don't have experience in a 12" tall tank with them, so I too would be interested to see PAR #s. Blindly, without PAR readings, I would be tempted to go 6 hours on the second channel instead of 4.

There is a possibility that the patches are from something other than lighting.

What are your parameters for:
Salinity
Alk
Temp
Nitrate
Phosphate

Any chance there are pests? Maybe a fish or invert nipping?

 

[Mark_C]

Going to rent a PAR tomorrow and run reading on the individual lamps, then pairs, then quads at surface level, 6", and 12".
As I only have Coral +, actinic, blue+, and special blue I may also pick up a few different bulbs if available and test those as well. Will post results here and in the PAR thread.

Parameters - 78F, 1.026SG, 7.9dKH (i hover around here +/- 0.02), nitrate & phosphate I just realized is way out of date (will pick up a new kit this afternoon).
Doing a 10% change every 2 days for past 6 days as well.

I shouldn't have any pests as an established tank with no new pieces and have been keeping an eye on the fish. The loos patterns on the corals seem random though. Small superman monti frag totally dead, chili monti next to it has some loss of color in center. A purple stylo that always did well high up with LEDS is in the top half of the tank and is dying upwards from the base while a green acro next to it is growing wildly. Trumpet sprouted 3 new heads in a couple weeks while small hammer died.
There's been no change in levels or positions, just the switch to T5 from LED. Odd how some are taking off and others dying out.

 

[Mark_C]

So with my current 4 bulb T5 setup, the top of my tank is sitting in about 380 PAR, the bottom around 180. Wee bit too high.
If I remove 2 bulbs, the top drops to 160ish. BIt too low.
If I try to run 3 bulbs, which would be perfect, no dice, the circuit on the light runs bulbs in pairs.

HAs anyone ever built a T5 diffuser?

My light has a plastic cover between the bulbs and the tank.
Thinking of getting some glass frosting tape, or something like that, and trying to use it on the plastic to diffuse a bulb, or 2, or 3-4, to drop PAR a bit.

Anyone tried this before?

 

[A. grandis]

Absolutely nothing to do with your light unless you shocked them.
If the LEDs were weak and you exchanged for the T5s without adapting them, then that's it!
Why so many water changes?
Pictures, please.

 

[Mark_C]

I doing the WCs as I lost a fish with no body recovery and to be honest, just because I can easily. Normally I’ll do a 2g change twice a week.

I did move from LED. I ran 2 of the T5 bulbs for 6 hrs a day for a week and brought them up an hour a week, eventually phasing in the other 2 bulbs for a few hours.

If PAR seems reasonable and parameters are good I’m going to have to do some research into schedules.

 

[Mark_C]

So, to dampen PAR a little (shout out to Mark at Ultimate Corals! Thanks!) I took a piece of fiberglass screening and mounted it to the splash guard of the T5 unit. After experimenting with a few sizes, I found a 12" long 3" wide strip, taped directly to the middle 3rd of the splash guard diffused the light nicely.

Top numbers are pre-screen
Bottom numbers are screen in place...

Thanks for the help folks.
Now, If anyone has a suggested lighting schedule for a 36" 4 bulb system...

 

[nereefpat]

Now, If anyone has a suggested lighting schedule for a 36" 4 bulb system...

8-10 hours on, then off

 

[A. grandis]

So, to dampen PAR a little (shout out to Mark at Ultimate Corals! Thanks!) I took a piece of fiberglass screening and mounted it to the splash guard of the T5 unit. After experimenting with a few sizes, I found a 12" long 3" wide strip, taped directly to the middle 3rd of the splash guard diffused the light nicely.

Top numbers are pre-screen
Bottom numbers are screen in place...

Thanks for the help folks.
Now, If anyone has a suggested lighting schedule for a 36" 4 bulb system...

You don't need any screen to filter the T5s at all. Just get to less hours a day and bring it up 1 hour every 2 days or so, if that is the problem. You are wasting the whole deal with the fixture which is to be efficient using all the light you can with those reflectors.
Bring it down to 4 hours a day. Every 2 days add an hour to it. Final photoperiod could be between 8 to 10 hours a day.