Write-Up Wednesday: Glass Tops On Saltwater Tanks
Using glass tops on a saltwater tank serves two main purposes:
- Keep fish in
- Cut down on evaporation
Keep Nemo in his house
Keeping fish in your saltwater tank is vitally important and yes, some saltwater fish are prone to jumping. Dartfish, triggerfish, firefish, midas blennies, wrasses, and anthias are all common saltwater fish that often test their carpet surfing abilities.
No matter how skilled the fish, they aren’t going to pass through glass and make it out of your tank. Unless they go through the one shortcoming of many glass tops: the last four inches.
Most glass tops leave about 4” of the back of the tank uncovered. They do this to allow room for any plumbing lines or hang on the back filtration. Often the glass tops will come with plastic that will cover this last 4” and can be trimmed to fit around plumbing or filtration.
Leaving the plastic piece off will allow for an easy escape for fish. And as I’ve said many times before, if there is a way out, fish will magically find it.
If you are using a canopy, then there isn’t a need for glass tops on your tank for purpose of keeping the fish in tank. However, the second reason for glass tops may be right up your alley.
Reduction of evaporation
Looking to reduce the amount of water that evaporates out of your saltwater tank? Using glass tops to cover the top of your tank goes a long way to cutting down on water loss. Unlike mesh or screen tops that keep the fish in, but let air flow through, glass tops massively restrict airflow at the water surface. Less airflow means less evaporation.
Warmer tank temperatures often accompany glass tops as restricted airflow means more heat build up. If you live in a warm climate and are going to use glass tops, be ready to manage your tank’s temperature through cooling fans or a chiller. This fact is especially true if you are going to use lighting such as metal halides or T5s that let off a lot of heat.
While glass tops are very effective at keeping fish in your tank and cutting down on evaporation, they are salt creep magnets. Glass tops will need frequent cleaning and can build up scum that can only be scraped off with razor blades or vinegar baths.
Glass tops will also reduce the amount of light getting into your tank so if you have dimmable lighting and are going to use glass tops, turn your lights up to make up for the loss of light. Also keep in mind that the dirtier the glass gets, the more light be shut out of your tank.
Of all my saltwater tank builds, I’ve only utilized glass tops once. However, I regularly use glass tops on quarantine tanks as they do a great job of keeping the fish in and cutting down on water evaporation.
Browse the Store! Questions?
What about gas exchange not being able to escape? Should you use an ammonia detector if you have a glass top? I was told that it’s best to remove it for that reason and use a screen. Also when I had the glass top there was always a heavy condensation build up that did cut back on lighting quite a bit.
I used to use the glass tops that came with my tank. In addition to limiting evaporation, causing copious amounts of condensate to build up on the inside tops of the glass, the temperature of the tank would steadily increase. If you are concerned about your fish jumping out (even a canopy won’t stop that) pick up some of the 1/4″ x 1/4″ clear fish net/screen that Bulk Reef sells and make the applicable window screen frames for your tank.
You get your cooling/evaporation/gas exchange/light without having to worry about making fish sticks.
Great points Mark, I also find the glass tops keep my lights free from salt creep. My lights hang rather low because I have a low profile canopy. I clean the glass tops every few days and everyone in the tank is happy.
If you have a sump Timothy (which you should) then you there’s no worry about gas exchange
Seems like without the canopy too much light would escape into the room…guess OK unless it is like my 180 gal. reef directly under my 65 in. Sony in my living room 🙂
Thanks Paul. I do have a sump on my 100 gal but I have a 30 gal QT that I just started using. I made a screen but I do loose a lot of water. Also put a circulating pump in there and an ammonia detector. Really don’t need the lighting so much. I was more concerned about the gases on a covered tank causing issues.
I don’t have a glass lid, just a screened in canopy on my 75 gallon with 20 gallon sump. I lose over a gallon of water to evap. a day! This is easy to measure using the auto-top off RO/DI tank. For me, the trade off of cleaning the glass lid frequently wasn’t worth it. Besides, here in very dry Colorado, a little extra humidity is nice.
I never got over the loss of my favorite clownfish that ended up on the floor the one day I removed the rear glass covers. From then on I keep the rear glass on but keep the front open. They’ll just bounce off the front canopy and land back in the tank embarrassed with a headache. Lol
I guess I’ve been lucky. My plastic strip that covered the last 4″ got so brittle and yellow that when I switched from T5 to LED’s I removed the glass (and plastic strip) all together. So far (over a year now) I haven’t had a jumper…
Mark does this also need to be for QT tanks?
I would like to know if there is an easy way to cut down on condensation, such as a double pain, etc. Currently use a kissel and with all the condensation I get no shimmer, boo!
Pete try slightly raising back or front side of top glass so glass slightly angled and drips of condensate roll away. you dont need much of an angle to do this!
use small silicone stoppers or even a cured strip of silicon to achieve this
Paul, just wanted to say thanks.
On my 29 Gallon Biocube with a 150 watt metal halide and led’s if I do not use the glass top my corals get very angry, it will take 3 days for some of them to come back out if I leave the glass off.
Also to change the subject for a second, I have been getting my filtered water from a local water store that has many stages of purifying the water, if I pay 10 more cents a gallon I can get one more process done to the water which is Ozone, can someone comment if there is a benefit to using water for making up my salt to have been ozone treated first? I do not have any fish in my reef tank, just SPS and and many other kinds of corals.
Thanks.