Halides and Acrylic

[Andrew17030]

I have a 120 quarter hex. I have 2 pfo 400 watt pendants. The opening on my tank is about 20x14, roughly the size of one of the pendants. It will obviously obstruct a bit of light. My questions are, will it make a significant difference if my halide light, is lighting through acrylic. The second is can and should I think about making the hole a little bigger. The tank is empty now.

[DSR]

I wouldn't use halides on an acrylic tank because of the heat that it puts off. There are numerous stories of acrylic tanks opening up under MH lights... Is your tank new? If so, check the warranty and/or call the manufacturer. I think this could be a road to a wet floor.

[n00by]

It makes sense but it's hard to believe that a tank, (be it acrylic or whatever), can withstand enormous amounts of weight from water but can't handle the heat from a MH,.

Acrylic tanks don't have seems, do they? It's just once big crafted peice?

[DSR]

No the have seams. Or, I should say, some do. My freshwater acrylic has seams on the back, top and bottom.

[der_wille_zur_macht]

Acrylic tanks are indeed assembled from flat sheet goods, but they should NOT have "seams" in any sense. The panels are solvent welded together, and if done correctly, the joint is literally stronger than the surrounding material in many cases. If your acrylic tank breaks, it shouldn't break where panels have been joined. If it does, it was probably not put together correctly.

That said, many, many, many hobbyists use MH over acrylic tanks. As with any other combination of lighting and tank material, it's not a problem if done correctly. MH does indeed put out a lot of heat, but not really THAT much more than other lighting technologies capable of the same output. Through careful design, it would be easy to minimize the impact - keep the lights higher up, use a sheild, cooling fans, etc. It's easy to get a MH rig to run at or below the temperature of other lighting rigs, if you design it correctly.

Can you explain the dimensions of your tank a little more clearly? I'm not sure what the typical layout of a "quarter hex" is. At any rate, do NOT consider making the opening larger, the bracing around the tank is designed carefully to meet the structural requirements for holding all that water in, and it is critical to keep the panels from bowing significantly.

[n00by]

Originally posted by der_wille_zur_macht
Acrylic tanks are indeed assembled from flat sheet goods, but they should NOT have "seams" in any sense. The panels are solvent welded together, and if done correctly, the joint is literally stronger than the surrounding material in many cases. If your acrylic tank breaks, it shouldn't break where panels have been joined. If it does, it was probably not put together correctly.

That said, many, many, many hobbyists use MH over acrylic tanks. As with any other combination of lighting and tank material, it's not a problem if done correctly. MH does indeed put out a lot of heat, but not really THAT much more than other lighting technologies capable of the same output. Through careful design, it would be easy to minimize the impact - keep the lights higher up, use a sheild, cooling fans, etc. It's easy to get a MH rig to run at or below the temperature of other lighting rigs, if you design it correctly.

Can you explain the dimensions of your tank a little more clearly? I'm not sure what the typical layout of a "quarter hex" is. At any rate, do NOT consider making the opening larger, the bracing around the tank is designed carefully to meet the structural requirements for holding all that water in, and it is critical to keep the panels from bowing significantly.

Well said. I wish I got an acrylic tank now that I think of it. Is there a big weight difference between 2 equally sized tanks?

[der_wille_zur_macht]

Acrylic is almost always lighter when considering empty tank weight, but IMHO it really doesn't matter since tank weight is only a fraction of overall system weight. The only time tank weight would be a big deal would be on a larger tank that you knew you were going to have to move often.

Keep in mind that acrylic also scratches extremely easily. I don't know if I would ever be able to live with an acrylic tank for simply that reason. IMHO glass is great for smaller tanks, and plywood is great for really big stuff. Acrylic is great for building sumps, filters, skimmers, etc - but it's just not my taste for a display tank.

[n00by]

I agree on the scratching part but it does make your DT look bigger.

Next time I get a tank it will be acrylic. Cost wise, cheaper, more expensive?

[WaterKeeper]

I have yet to see a post on this forum about a melted acrylic tank. They must post those on the Advanced Forum.

[DSR]

That is good to know... (from my perspective... not from my wifes). The information I had made reference to earlier was from another forum concerning a fella that put MH over his tank and it basically came apart. he attempted to return it saying that it was defective and they said no because of the mh light. So maybe his was defective afterall. I am glad to hear that it can work. I really want to set up my 29 gal acrylic for clams and such, but wasn't going to try because of the lack fo light.

[WaterKeeper]

I should add in that if the MH are unshielded, double ended, then they need a piece of glass to cover the MH tube. They emit harmful UV and can create problems for you livestock, and one's eyes, as acrylic does not greatly reduce low end UV radiation.

[der_wille_zur_macht]

Originally posted by n00by
I agree on the scratching part but it does make your DT look bigger.

I guess that's subjective. Personally, I don't like the look of solvent-welded corners on a DT, even if they're done really well. I *love* the look of black silicone, though.

Next time I get a tank it will be acrylic. Cost wise, cheaper, more expensive?

In many cases, probably more expensive. For most "average" tank sizes (say, 50 - 150 gallons), probably about 50% - 100% more than a plain old glass tank.

The information I had made reference to earlier was from another forum concerning a fella that put MH over his tank and it basically came apart. he attempted to return it saying that it was defective and they said no because of the mh light. So maybe his was defective afterall.

It's really hard to guess 4th hand, but there could have been all sorts of circumstances involved - incorrect tank construction, or what if he had taken powerful MH pendants and set them right on top of the eurobracing? That would certainly ruin any tank, regardless of the material or construction method.