Glass tops

[duc]

This might have been discussed 100 times but how much light do you reckon glass tops block/reflect? How about the plastic grid stuff? I have to keep a cat out of the tank so I need something and I am wondering if the plastic will allow a lot more than the glass or just a bit.
Thanks
Clif

[MikeDeL]

http://www.maast.org/index.php?name=PNphpBB2&file=viewtopic&t=9196&star t=40
Read the 2nd post on this page.

[duc]

Very interesting so screen would be better than eggcrate buy how about glass? Glass should be less than both.

[AlexKilpatrick]

The numbers in that post seem really high to me. I'm wondering whether there wasn't some other issue in that test.

I agree with you. I don't think glass would block much at all. You could always bump up to 400's if you needed to. The main issue I see would be heat. Tanks lose a lot through the surface area of the top, and you would be holding all that heat in. But it would cut down on your evaporation quite a bit. :)

[Ram_Puppy]

I could be wrong, but I think Glass blocks light on the hotter end of the spectrum, not totally by any means, but it reduced what is hitting your water.

I don't think there are any other issues witht that test alex, They used that Lux meter on the cube tank by the front, and readusted the lights accordingly, it looks totally amazing now. remember also that from a MH point source light, light is not going straight down, it is traveling at an angle, intercepting a completely verticle surface, it makes total sense to me that that much light is being lost.

[GaryP]

The other issue is maintenance. Obviously glass gets salt and other stuff on it. This stuff cuts down on light transmission. How often do folks clean it.

gary

[AlexKilpatrick]

I have no experience in this area. Is the LUX meter waterproof? It seems you would have to be in the water. If you try to measure it from outside the tank, you are going through glass. If you put the LUX meter in a baggie, then you are going through plastic.

With respect to the eggcrate, I am thinking of it this way. Eggcrate is (guessing) about 4 or 5% stuff and 95% air. If you held it under a MH that was just sitting out by itself, you would get a shadow grid that was thicker than the orginal grid. But I can't imagine the shadow would cover up 40% of the surface. I don't have any eggcrate, or I would try it.

Now, with respect to the glass, here is something else to think about. If you have HQI lights, the light is already going through one pane of glass, in order to block dangerous UV. Another pane of glass might block a bit of the light, but it isn't going to block *more* of the spectrum than the glass on the HQI lights.

I do agree it will get gunky, and it won't be any fun to clean.

[Ram_Puppy]

good point gary, I hadn't thought ab out that since I took off my salt creep covered glass top a few months ago! :)

Alex, don't think about how much light is being blocked by the surface area as you see it looking directly down, think of it this way...

if you were to hold a small piece of egg crate up infront of your face and look direcly through it, not much of your vision would be blocked, but, if you were to rotate that egg crate to a slight angle, your line of sight would begin to decrease, eventually, you will hit an angle where the egg crate causes 100% obstruction to your LOS. Metal Halides being a Point Source of light, will run into the same issue, though, I suspect VHO's, PC< and T5's would not suffer as much since they are more spread out.

[AlexKilpatrick]

Ooooh. Thouht experiments. I love those. They are much less messy than real experiments. :)

I agree that if you tilt the eggcrate, you will get to a point to where you can't see anything.

However, try this thought experiment. Hold a piece of eggcrate out in front of you, at about 1' (typical distance for lights). Close one eye. Now, you have a "point receptor" which is analogous to a point source of light. If the eggcrate is perpendicular to your line of sight (as it would be on an aquarium), then I think you would be able to see pretty well. Flourescents would be even better, of course.

The real way to do this experiemt is to take an aquarium and cover half with eggcrate (or whatever). Put two identical corals on each side and see how they do.

[Ram_Puppy]

even that experiment would be anecdotal, different flow, 1 ballast could burn harder than the other, bulbs may not be equal...

of course the light right under the bulb is going to get through, you can't have a static measurement across the surface of the water, lux is going to drop off naturally as you move further and further away, I think the point is, that light drops of drastically fast with egg crate.

[Instar]

Glass cuts out a little more than the eggcrate but not by much, but, it may not be picked up proportionately by a general light meter measurement. A thin clear plexiglass cuts the least, about 8 to 10% but still can result in a noticable shift of coral colors over time under something like pc's. Acrylic from something like 10% to 14% if its clear and depending on the thickness. I cured my cat by letting him fall in. He doesn't do that anymore. For tanks with jumpers, I would use walls and slides to get them to fall back into the tank. Imagine the concussion if they jump straight up and hit glass right after they leave the water? The next alternative for jumpers for me would be relatively thin plexiglass. Its cheap and if it gets to a point that cleaning is useless, it can be replaced.

[::pete::]

.... are you trying to stay a way from a canopy to keep the cat out?

[duc]

.... are you trying to stay a way from a canopy to keep the cat out?
I actually hadn't thought about a canopy until you just mentioned it, with a canopy I could go topless and keep the cat out.
Hmm now my mind is working and my wallet is screaming.
Clif

[GaryP]

Personally I think the biggest issue with a glass top is heat transfer. Remember you are cooling the tank by evaporation. A tank operates like a big swamp cooler. No evaporation, no cooling, unless you are running a chiller. The last time I checked, water was a lot cheaper than the electricity to operate a chiller and a lot more recycleable.

I have cats fall into a tank... once. They like to sleep on top of my hood and one jumped up onto the top of the tank when I had the hood off, replacing lamps. After they spend a day or so licking the saltwater off their fur they will never do it again.

Gary

[duc]

Personally I think the biggest issue with a glass top is heat transfer. Remember you are cooling the tank by evaporation. A tank operates like a big swamp cooler. No evaporation, no cooling, unless you are running a chiller. The last time I checked, water was a lot cheaper than the electricity to operate a chiller and a lot more recycleable.

I have cats fall into a tank... once. They like to sleep on top of my hood and one jumped up onto the top of the tank when I had the hood off, replacing lamps. After they spend a day or so licking the saltwater off their fur they will never do it again.

Gary
If you remember an earlier post by me my cat jumped into the tank while I was setting it up (Funny, I still laugh about it). She has just started getting on the tank after two weeks, but what about cat hair, dust, etc.? Also the tops seriously muffle the overflow noise, which is pretty noisy depending on your setup.
Clif

[GaryP]

I have cooling fans on my tank hoods and I have to clean them every couple of months. The fans get coated with a layer of dust and it throws them off balance and can cause the bearings to burn out. As I said, my cats like sleeping on top of my hoods because its warm.

I don't think that hair or dust causes any appreciable problem with the tank.

Gary

[duc]

I don't think that hair or dust causes any appreciable problem with the tank.

Gary
I will remove the tops this weekend and show the cat, we will see how it goes. I opened one up last night and put the light over the pen hole, it was a very noticeable difference.
Clif

[GaryP]

Dip his paw into the tank. I think that will solve the problem.

Gary

[john]

I have cats fall into a tank... once. They like to sleep on top of my hood and one jumped up onto the top of the tank when I had the hood off, replacing lamps. After they spend a day or so licking the saltwater off their fur they will never do it again.
Gary

Just curious if anything happened to the tank..

[GaryP]

Nope. Some water splashed out.

Gary

[Instar]

My cat just came home from the vet. It was shampoo'ed and flea dipped. The smell of the flea dip was very strong. I put him down and did something else. When I looked at the cat he was all nice and clean sitting in a puddle of salt water on the kitchen floor. Little thing jumped into the sump to wash off the flea dip. I wrote the entire sps reef off as dead. AFter 2 days and no ill effects, I figured I better run some carbon on there and get it out and do a water change. Didn't hurt anything in the reef, fish, corals or inverts. If the sump is setup correctly, any dust or hair gets caught in the fibre mat or sock filter and does not return to the tank.

[duc]

Now that story beats watching TV, very entertaining.
I pulled my tops off and let the cat know/show, got my fingers crossed. My main concern is not the water or the cat as individuals but if the cat jumps up on top falling in and dragging a light or 2-4 with her. That could turn out real ugly.
Clif