polarbear Posted September 30, 2009 Share Posted September 30, 2009 I am going to be putting a 150w 14k MH light on my 29 gallon biocube. I dont want the water to evaporate since I will have to remove the top with the stock lighting in it. I was thinking about getting a piece of glass or acrylic made to fit the top of the tank. I was also thinking about cutting the middle out of the lid of the biocube but didnt know if the heat would melt the remaining plactis part. I would cut enough out from around it but still wasnt sure. Any suggestions on what I should do. I already have enough evaporation as it is becuase of the refugium so I was wanting to do whatever possible to keep this from happening more. Thanks for the help. Quote Link to comment Share on other sites More sharing options...
+Daniel Posted September 30, 2009 Share Posted September 30, 2009 I think you risk trapping heat beneath the glass. The reason why the water evaporates is because those molecules are getting too hot (they have too much energy) and end up moving into the gas phase (and they remove a lot of heat in doing so). Also, you'll reduce your light output by two ways: the glass itself reduces the PAR and the water droplets that will eventually form on the underside of the glass will further reduce the PAR. A refrigeration-based chiller (not fans) is the only way to reduce evaporation, while still keeping your tank temperature stable. Alternatively, this probably isn't feasible or sensible, but if your ambient air temperate were low, while the humidity remained high, you could avoid excessive evaporation-- but high humidity isn't very comfortable and tends to grow mold. ha. So my point, I think, is that you should probably try to embrace water top offs which can be done easily with an auto topoff device. Quote Link to comment Share on other sites More sharing options...
polarbear Posted October 1, 2009 Author Share Posted October 1, 2009 Thank you so much for your input. It's helpful Quote Link to comment Share on other sites More sharing options...
polarbear Posted October 1, 2009 Author Share Posted October 1, 2009 should I still run a heater with the MH light? Quote Link to comment Share on other sites More sharing options...
Gonzobob Posted October 1, 2009 Share Posted October 1, 2009 Yes, keep in mind that when the lights are off the temp will drop. I use a fan that comes on with the halides to keep the temp from rising. Quote Link to comment Share on other sites More sharing options...
NonSequitur Posted October 1, 2009 Share Posted October 1, 2009 Yes, a heater is helpful to keep the temp from dropping too much when the halides are off. When I first installed mine, I was seeing daytime highs around 84-86 (too high, IMHO), dropping to 78 at night. This was too much of a swing, so I added more fans to the tank during the time the lights are on. This kept the daytime temp around 78, but the nighttime temp has been dropping to 74 or so lately since I keep the house cooler when the outside temp is cooler. Still too much of a swing. Now I run a small heater (50w) set at 78 at night, plus added a bigger CF lamp (26w 150w equivalent) to my fuge on an inverse photocycle to add heat to the tank when the halides are off and the room temp is lower. So far so good. Quote Link to comment Share on other sites More sharing options...
polarbear Posted October 1, 2009 Author Share Posted October 1, 2009 do you think the stock fan on a 150 w 14k MH light will do the trick on cooling the tank or should i invest in some more fans. thish is for my 29 gallon biocube. Also I was thinking of cutting a rectangle whole out of the stick hood along with cut outs on each side for the legs of the light to sit on the top. What do you think about this. here is a crapy picture of what I thinking about doing. What I really want to know is if the MH light will melt the surrounding plastic. It would be a good inch or two from the side of the light fixture. tank.bmp Quote Link to comment Share on other sites More sharing options...
polarbear Posted October 1, 2009 Author Share Posted October 1, 2009 Quote Link to comment Share on other sites More sharing options...
NonSequitur Posted October 1, 2009 Share Posted October 1, 2009 I suspect you'll need at least one more fan (and possibly more), blowing on the surface of the water and promoting evaporation to keep everything cool. Doesn't have to be anything fancy, though.. an old computer fan connected to an appropriately sized wall wart transformer will work in a pinch, as will one of those cheap clip-on fans they sell at walmart (just make sure it doesn't fall into the tank, thesanfords lost almost everything in their tank when a 120v fan fell into their tank.) You can always experiment this way, then make it permanent/pretty once you see how much airflow you actually need in your application. Quote Link to comment Share on other sites More sharing options...
NonSequitur Posted October 1, 2009 Share Posted October 1, 2009 My other suggestion: invest in some sort of auto top off and embrace evaporative cooling. Way cheaper than a chiller both to set up, and in electricity costs to run it. About $50 from autotopoff.com will get you a single float swich and an aqualifter pump, and with appropriately sized reservoir for topoff water you won't have to worry about evaporation. I'm probably going to go that route to automate my top-offs/kalk drip once I have some more cash in my tank fund. Quote Link to comment Share on other sites More sharing options...
polarbear Posted October 1, 2009 Author Share Posted October 1, 2009 (edited) thanks for the input. i do wnat to get a top off as well. What do you think about the hood mod for the lighting. I wanted to keep the hood on becuase I like the look but mostly becuase I have a dog that sheads a lot and hair gets into the tank sometimes (just think how bad it would be with no top on it). the water will still evaporat. I would also leave in the stock fans that come with the biocube. My concern is the MH light will melt the plastic hood even though its not touching. Im new to MH lights and am not sure on a lot of things. Edited October 1, 2009 by polarbear Quote Link to comment Share on other sites More sharing options...
+Daniel Posted October 1, 2009 Share Posted October 1, 2009 You should not keep a MH that close to the water-- 1) that's probably too much light and 2) you risk melting the plastic. Generally, halides should be kept ~4+ inches from the water line (usually more!). With that being said, the plastic should be okay if there are several inches between-- one inch will not suffice, in my opinion. Instead of modifying the original hood, which you could potentially sell for some extra $$$, why not consider a custom canopy? It might look a little better than a modified stock canopy. Quote Link to comment Share on other sites More sharing options...
NonSequitur Posted October 2, 2009 Share Posted October 2, 2009 In my experience, as long as the lamp is more than a couple of inches from the plastic it should be ok. . If the light is immediately over the plastic, it will definitely melt it, but the way you have it it set it should be ok. Daniel makes a good point about the proximity of the lamps to the water.. the closer the lamps are the more heat will be transmitted to the water, and the more salt creep you'll have to worry about cleaning off of the lamp (or uv filter glass in the case of DE lamps) Quote Link to comment Share on other sites More sharing options...
polarbear Posted October 2, 2009 Author Share Posted October 2, 2009 Thanks again for your input. It helps out a lot. The light will be about 4 to 5 inches off the surface of the water. Quote Link to comment Share on other sites More sharing options...
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