Adding MH on Acrylic?

[pch90265]

Anyone have input on how 3 x 250W DE MHs might affect the bond on the top brace of an acrylic tank if they were 6-8" from the tank? Don't want my tank delaminating . . .

My tank is an Envision Acrylics 275W -- 82" w x 32" d x 28" h -- 3/4" cell cast acrylic. I'm using 1/2" Lucite covers set on 1/2" feet... the fixture will sit on 6" legs above the covers.

I'm looking at the Sunlight Supply Co Maristar 3 x 250W MH + 4 x 39W T5 combo fixture. Love the TekLight T-5's I'm running now, but when I add a second row of them (front to back) I don't want a 6" dead spot the length of the tank where the two frames bump together, so I'm adding the MH for wider throw.


Thanks all,
Sean

 

[juststartingout]

I would call James and ask him.

 

[blufyre3]

Imput: Your daughter is a living doll. grandma's know these things.

 

[blufyre3]

Sorry, forgot to reply. I have a tenecor acrilic tank w/ 5 Current Outer Orbit Model 1040. Each on has a 10,000K metal halide. They are about 18 inches above tank and I haven't had any issues. They've been over the tank for about 1 year and 10 months. However, I also think you should check with the manufacter.

 

[ppht]

My Maristar cracked My top glass but I had it too close. I moved it about 8-9 inches up. I have 2 250watt MH 14K

 

[Acrylics]

Hi Sean,
Feel free to use MH on the tank provided the bulbs are not directly over the structure, ie the top bracing or flange, it's also recommended the main areas of the reflectors are not over the acrylic but a little overhang by a large refector is fine. The tank's joints will not be affected in any way, the only problem folks have is that the bracing can heat up too much and become weak if the bulbs are directly over the acrylic. This is especially true in an underbuilt tank or in a tank with sharp radii in the access cutouts as the stresses are more concentrated in these spots. I know your tank fairly well and would say that your tank fits neither of these If you follow the above guideline - you will not have any problems in this regard.
Do monitor the bracing temps though (if you don't mind), maybe one of those cheapo thermometers on the acrylic. The working temp for acrylic under load should run around 140F or so.

Your acrylic covers may warp out due to intense direct radiation but those are easy to replace and will provide excellent insulation.

HTH,
James

 

[pch90265]

Hey James!!! Glad to hear from you... i was hoping i'd hear back from u on this thread since i hadn't heard back on the email i sent a couple weeks back -- i know you and email are about like me and voicemail . . .

One point of reference -- I just used a babythermometer and measured both top braces that are 1" air gap directly under the T-5 fixtures/bulbs. They are both ~109F with the lights having been on 3 hours. I'll measure them a few more times today, and, yes, I've put a cheapo aquarium thermometer I have lying around on one brace to see what it does over the course of the day.

The lucite covers are MUCH warmer, at ~130F. They are, as predicted, acting as effective heat sinks. I've put half-round feet on both sides of the covers, and flip them every other week, or so -- that has effectively bowed them back into shape every other flip.

The genesis of this thread is that I've noticed the two center braces have bowed by about 1/8"... when I took the lights/covers off last weekend for cleaning I noticed it. They've bowed up, away from the water surface, in exactly the manner you described the covers would. Anything to worry about there? I can certainly raise the T-5's onto legs when I get the combo fixture -- they'll be lighting coral areas of the tank that haven't been directly lit, to date . . .

Thanks, as always, for the insights.

--Sean--

 

[Acrylics]

Oh, oops, I had put that emai in the saved folder and never got back to it, will do so this weekend.
The slight deflection in the bracing is fine, no worries. Just moisture absorption at work.
The 109F reading is good, means everything you have been doing is working as expected
If the covers get too warped out or won't clean up, lemme know.
As an off question; what's your evaporation rate at now in the new climate?

Hope all is well,
James

 

[pch90265]

All is very well, thanks...!!!

The covers are working great, I hope they last another 4-5 years... no craze issues, fogging, etc. I try to monkey in the tank as little as possible, so they are relatively scratch free too.

Evap has been a non-issue, and I've been surprised by it. I'm running at about 7-10 G / week on 500 runing gallons of sump/display/fuge. I consider that pretty darned low. A good part of that, no dount, is having covers on all three systems...

I've been keeping reads on the utility room moisture vs. the rest of the house vs. ambient air outside, and I'm running 0-5% above ambient in the house (without the A/C running this summer, or the humidifier running last spring) and 5-10% above ambient in the utility room. Again, I think that's miniscule compared to some of the nightmare conditions I've heard of on R/C.

One big reason I think that is working out well -- aside from the naturally dry climate -- is that the cold air return for the central air system is right next to the tank, and near ground level. Humid, cooling air is getting sucked into the heat/air-conditioner circuit, and getting dehumidified on both cycles. The minimal additional bump didn't get us above 50% humidity all summer, and has kept us above 10% all winter -- which is nice when the ambient drops to single digits!

--SM--