Evaporation Reduction

[warden13]

I have recently upgraded from a 30 gal which had a glass covering to a 55 gal without any cover or hood. I have noticed an increase in evaporation due to not having a cover and salt has covered my light. I was thinking about getting another glass cover or maybe an acrylic cover. I know this will reduce my lighting but I think it's already reduced due to the accumulation of salt on my light lens. I am looking for any pros or cons for glass vs. acrylic or any other ideas. A point in the right direction on where to buy any suggested covers would be GREATLY appreciated.

[Entropy]

Honestly I would just clean the bulbs more often. Glass covers cause more problems than they solve, and I would only use them if you have a tank full of jumpers (fish).

[balberth]

I have an acrylic cover on my 180 gallon, mostly to reduce evaporation into the house and prevent jumping fish. Some observations:

- The acrylic warps a bit, both due to heat from the MH lighting and absorption of moisture on one side. It still works.

- Acrylic absorbs quite a bit of UV, it's not entirely clear how this is different from glass or whether this is a problem. I got some special UV transparent acrylic and this seemed to make a small difference in coral coloration under my 400W SE MH, but not much.

- Covering the top prevents excessive evaporation, but it also means that the tank is much easier to overheat. I have to run a chiller, and probably would not need to if the tank were not covered.

- Covering the tank discourages maintenance - it's another layer to get off, so any quick little thing now takes more time and effort.

- As for salt creep and cleaning, in my situation this has not been a big issue. I get some condensation when the lights are off, but that is evaporated when the lights come on. Moreover, the condensation is basically pure - not salt water. Not a lot of salt gets on the acrylic, and I have not had to clean it off more than once a month or so. On the other hand, I don't have a whole lot of surface agitation.

--Albert

[warden13]

Those are some great points balberth. I don't want to purchase a cover and possible chiller because I don't want to buy more RO water. Maybe I just need to move my light higher to avoid the salt problem. Thanks

[jacmyoung]

The salt deposits are likely the result of the surface agitation and saltwater droplets dancing around a few inches above water level.

[lawmary]

I have an open tank with a polyp light fixture sitting on the middle top of the tank, and I lost a few clownfish jumping out. I now use a white plastic grate material over the open areas. It comes in a big sheet and you can get it at Lowe's or Home Depot. I just cut it into three strips, one long one for the open side and two shorter pieces for the side with the overflow. I don't get much salt creep on the light and I just wipe it once a month. I don't have any surface agitation in my main tank. Underneath the tank around my refugium, I get a lot more salt creep because I have a lot more surface agitation from the inflow pipe at the surface, so I agree that surface agitation causes a lot more salt creep. I do have to add RO water daily to the tank because of evaporation. Hope this helps.

[atlfishes]

I made some custom glass covers from lowes to fit on top of my tank. This stuff is a bargin. I have two sheets and leave a little space between them and on the edges of the tank, which allows for heat to escape. All I have is 2 90 watt PCs and the temp of my tank hasn't been effected at all. We'll see in the summer.