Tragedy in acrylic tank w/metal halide lights!

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AC Members
Nov 29, 2007
Northern Suburb of Atlanta
I purchased an acrylic 100 gallon Clarity Plus flat-back-hex aquarium in 1994. In 1997 I contacted the company to inquire about adding metal halide lights. They told me that I needed a higher canopy (which I purchased), and also a reliable fan. Everything worked perfect for 10 years...until 5 weeks ago.
On a Sunday morning, I noticed a puddle of water on my hardwood floor in front of my aquarium, about 2 feet in diameter. I could hear water running somewhere, and immediately noticed that the water was running out of the acrylic tank stand. I figured that a hose had burst, or my water makup line had ruptured, but never in my wildest imagination would I have guessed what had actually happened;
The seam where the back of the tank is cemented to the top of the tank had totally failed, except for about 3 inches on each side. The back of the aquarium was bowed out over an inch, but because the seam had held on both ends, the panel was cracked on each side about 4 inches from the top, and water was just gushing out of the cracks.
I was actually expecting the entire tank to just come apart at any moment, spilling the entire contents all over my kitchen.
I contacted the company the next day, and was told that the UV light from the metal halide bulbs had degraded the acrylic cement, and that metal halide lights are not recommended with acrylic tanks. I had never heard or read anything suggesting that metal halide lights would cause an acrylic tank to "come apart", but I have no reason not to believe what I was told.
I wish I had known so I could have been prepared, but am passing along the information in the hopes that those of you who have metal halide lights with acrylic tanks, ocassionally inspect the seams for integrity.


AC Members
Mar 18, 2006
San Angelo, TX

Hopefully some one else will "chime in here" if I am wrong.

Before I ordered MH for my acrylic tank I "checked into this" although very little information was available.

What I was able to deduce (which is hopefully correct) is that acrylic is inert with respect to electromagnetic radiation.

I did find that PVC is not inert with respect to "daylight" electromagnetic radiation.



AC Members
Feb 21, 2007
Princeton, NJ
I thought that the single ended bulbs had UV shielding built in, and that the DE bulbs used a glass shield over the reflector assembly that filtered the UV.

Either way, that's a bummer, man.

How does the story end?

What happened to the live stock?

Where do they live now?


The Old Guy
Oct 21, 2006
You're killing me! I had plans to use 3 MH 250s over my Clarity Plus. Now I wonder how many hundred T5's I'll need to keep sps:mad2:

Seriously, thanks for the heads up. I'll investigate this more and post my findings.


Nov 29, 2002
ST.Louis Area
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I do not doubt that the effects of the "heat" generated by the MH's assisted in your tank colapse. UV light is a degenerative force and affects all plastics.

However, your acrylic tank was 13 years old. Bowing of the plastics is inevitable. They will all bow sooner or later. If your tank did not have Eurobracing, then the bowing is worse and puts much more strain on the joints.

I have seen many acrylic tanks bow very badly, That is why they are made thicker now than they used to be and almost all offer Eurobracing. Warranties from acrylic manufacturers are always a joke. They always ask just enough questions of how you set up your tank to find a way of voiding them. Your tank was obviously out of warranty, but you see the trend.

Heat more than the UV caused your acrylic to compromise. Yes, the affects of UV and heat are much greater on PVC.(mentioned earlier). T5 HO 54w lamps with independant reflectors have the same PAR ratings as MH and grow SPS just fine without the heat.

If you insist on acrylic tanks, then make sure it is a thicker piece of acrylic, has Eurobracing, and that there are no cracks, webbing, or air bubbles in the seams.

IMO, Clarity Plus is not my favorite tank. I think if you got 13 years out of that tank you did very well.


AC Members
Jan 5, 2007
I have no words to say exactly how sorry I am. I was considering an acrylic just for a cange, but I will now stick with my glass tanks. Let me know how everything turns out.