glass tops - gas exchange

[Leko]

Standard glass tops (75 gallon)

Does anyone use these? I'm thinking about trying it.

An open top is the best for gas exchange but I'm wondering - the back edge on these glass tops are open about 4" and with the right "boiling" surface flow - can I get sufficient gas exchange. Helping this would be a fuge/skimmer in the sump that also exchanges gas.

What I get in return is less evaporation.

 

[ryanjohn1]

Glass will cloud up. Probably get salt creep and then probably grow some gross stuff on it unless you clean it daily

 

[mike550]

@Leko I have glass tops on my 120. Couple of things. First, the idea that gas exchange is reduced has no data. Just opinion. I would imagine that between surface agitation, the sump, and the skimmer there is plenty of gas exchange. It’s just like people who said glass lids would reduce light. Well someone did some experiments and figured out that’s light is reduced by a percent or two But nothing material. Second, Lids are easy to maintain. When I do water changes I remove them and wipe them down. Not a big deal. No clouding or gross stuff and I clean them about every three weeks.

Personally, I really like lids. I have limited evaporation from the tank (maybe a gallon every ten days) and no salt deposits on walls and stuff from evaporation. Plus I don’t have salt dust collecting on everything etc.

 

[exnisstech]

I used to run glass lids on a 150g and 180g. The 150 is gone but I no longer run them on the 180. There was never any issue with gas exchange and if your running a sump I doubt there ever would be. My problem is they are a total pita to keep clean. If you have coral they block a lot of light, especially when dirty which was always for me. They get salt creep and a lime like scale builds up on them. I'm open top now but I don't have jumpers. With the opening in the back tho they really aren't to good for jumpers anyway.

 

[hart24601]

As talked above above there are issues with maintenance keeping clean, but for gas exchange if using a skimmer and decent turnover I think it’s just a myth people parrot. Unless dosing chemiclean or something to impacts oxygen I have never heard of anyone losing livestock to low oxygen unless there is a power outage. 10s if not 100s of thousands of FW tanks have run glass lids for decades with heavier bioload than reef tanks and without skimmers and you don’t see issues either.