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how thick to prevent condensation?


miketron75

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lets say I want to go down to 55/60 degrees in a 75 deg room, what thickness glass or acrylic do I need to avoid condensation on the outside of the tank?....

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acrylic. for glass I would go thicker, or do a double-paned setup. acrylic would be my recommendation, though.

now my thoughts are on keeping socal tidepool critters is that 65/70 degrees should be plenty cold enough, I have kept bat stars, opel eyes, ocra stars, sea hares, snails and hermits at tropical temp, i sea these things hanging off rocks in 100 degree air temp. maybe I dont really need to go that cold. the only thing I couldnt keep at 77 degrees were sculpins...and I think they died not because it was too hot, but because colder water can hold more oxygen and they require alot. any thoughts?.

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100 degree air temp doesn't really mean anything. I grew up about two hundred feet from the la jolla tidepools, so I can tell you from experience that cold water rushes into those shallow pools with every tide. just because they can survive warmer temps in ther native habitat doesn't mean they can survive sustained warmer temps in an aquarium. if you want to keep local socal livestock for any length of time, the temp should be between 60 and 65.

 

honestly though, a standard acrylic aquarium would be fine except in cases of extreme humidity, ie heavy fog with the windows open.

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...just because they can survive warmer temps in ther native habitat doesn't mean they can survive sustained warmer temps in an aquarium. if you want to keep local socal livestock for any length of time, the temp should be between 60 and 65.

 

Tide pool animals are exposed to periodic temp spikes in the wild, but many probably can't take sustained temps above their natural monthly average temp range (58 degrees F in January, 68 degrees in August). I know that Catalina gobies die within a few months at reef tank temps, and anything that doesn't die above 68 is probably stressed, or at least living out it's life at an accelerated rate. I have a bimac octopus I keep between 56 and 62 degrees that is about two years old, which is much older than bimacs kept at room temp ever get. If you're going to keep so cal animals, please have a chiller, and keep them below 68 degrees (preferably 60-65).

 

I didn't want my chiller to need to be too big and expensive, or need to work too hard, so I insulated my tank with 3" of rigid Styrofoam insulation under the bottom, on the back, and on one side. The other two sides have double paned glass and the top is double paned acrylic (the insulated top is overkill for insulation, but it keeps my octopus from escaping).

 

Before I put on the 2nd pane, on my glass tank, I got a lot of condensation during humid months, but not much the rest of the year. My guess is that 1/2" acrylic would eliminate condensation, except for a very cold tank on a very humid day, but acrylic is still a lousy insulator that will cause your chiller to run a lot more, wear out sooner, use much more electricity, and dump a lot more hot air into the room, causing you to run an air conditioner to bring the room temp back down. I think a far better solution is to take a nice cheap glass tank and add a 2nd pane onto it yourself, with a 1/4" to 1/2" air space in between. I'm planning to set up a larger cold water tank soon, and I'm planning to find a used glass tank on Craigslist, and use 1/4" acrylic sheet, and 1/2" square acrylic rod (as a spacer) to make it double paned on three sides (then use Styrofoam on the bottom and back). It's easy to do if you know the tricks, which I've learned the hard way:

1) Silicone sealant won't stick to acrylic, and water vapor can move right through it (it's gas permeable) so don't use it to attach an acrylic rod (spacer) to a glass tank. Instead use "E-6000 Adhesive", which will bond well to both glass and acrylic, and dries clear and flexible, like silicone. It might also be gas permeable, but you can paint it after it cures, to seal out humidity. If you're putting a 2nd pane on an acrylic tank, just use weld-on, but do it right so it's air tight.

2) You need to make sure that the air trapped between the two panes is dust free and very dry. You can run an air filter, and an air conditioner or dehumidifier in the room for a few hours before you glue the 2nd pane on, and hope that the air that gets trapped inside is dry enough. If that doesn't work, or if you discover you've had a leak, and humid room air gets inside the pane, just remember that the air inside a scuba tank is very dry, and very clean (free from dust). When I got condensation inside my 2nd pane, I made two small holes in the spacer (one at each end of the tank), let air from a scuba tank seep slowly into the space between the panes through one hole, and exit out the other hole. After an hour or so all the condensation had dried, and all the moist air had been flushed out. I sealed the holes (and the original leak) and haven't had a problem.

3) If you want to get fancy, you can use argon (from a welding supply shop, or dive shop (used inside dry suites by tech divers) instead of air between the panes. Argon is a 40% better insulator than air.

4) I used 3/16" glass for my 2nd pane, but I worry about the green tint that glass has, so I think I'll use acrylic next time. However, acrylic is a lot more flexible and prone to bowing than glass, and I wonder if the acrylic will bow and distort the view of my tank as the temperature and/or barometric pressure fluctuate. If so, my plan will be to drill a small hole in the bottom acrylic spacer and run a small vent tube down into my stand to a half full Mylar balloon. As the air (or argon) between the panes expands or contracts, the balloon will fill or empty, but the pressure inside will always be equal to the pressure in the room, so the acrylic won't bow. I might even be able to use 3/16" acrylic instead of the more expensive 1/4" with this scheme.

 

FYI: 1/2" Acrylic insulates (resists heat transfer) about 5 times better than an equal thickness of glass, but 1/2" of air insulates 9 times better than 1/2" acrylic, and about 45 times better than 1/2" of glass. So while 1/2" acrylic will probably prevent most condensation, it will let nine times more heat leak in from the room than a tank with a 2nd pane would, and 1/2" acrylic costs a fortune.

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AquaticEngineer

I experimented with a few different thickness' of acrylic throughout this last summer on smaller tanks in my garage without chillers. While the 3/8 and 1/2 inch tanks didnt sweat much, they still did during the summer, and the temp fluctuated a lot.

 

I also have the benefit of having 2 marineland 110 gallon tanks plumbed into the system in my garage as the powerplant for filtration and chilling ;)

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