Oxygen Exchange???

[awestruck]

I posted this question once before and no one responded so I will try again. Some people say that in order for oxygen exchange to occur you cannot have a glass or a plastic lid on the tank; others say that you can have a lid on the tank because an oxygen exchange will occur as long as there is sufficient water movement at the surface. So, lid or no lid. What is the answer?

[xtrstangx]

No lid is better.

Yes, you can still get gas exchange with a lid, but its not nearly as effective as without. You can breath into a big paper sack, you do get some oxygen, but not enough, right?

[awestruck]

Thanx for your reply. Here is my next question which I should previously have asked: my lights are not hanging from the ceiling, so obviously they are sitting only slightly raised above the glass. What do I do, exactly, to ensure that they do not fall in the water?

[xtrstangx]

Originally posted by awestruck
Thanx for your reply. Here is my next question which I should previously have asked: my lights are not hanging from the ceiling, so obviously they are sitting only slightly raised above the glass. What do I do, exactly, to ensure that they do not fall in the water?

What kind of lights do you have?

If you have MH, find some way to get them up off the surface of the water by atleast 4", 6" is better. You may need to build a canopy or atleast make wood legs for them to raise up off of.

If you have PC's, T5's, or VHO's, see if the manufacturer sells legs that hook onto the fixture to raise it up. Otherwise, you'll need a canopy or make your own legs.

[awestruck]

Thank you!!! I have 1 T5, and 2 pc's. I have seen the legs at my LFS and that sounds like the best solution. I like the look of canopies but have no clue as to how to build one so again, the legs are probably my best bet. However, if there is no lid on the tank, do you need to top off more frequently due to evaportation? And, I don't have a real serious problem with algae but could there be a possible decrease in algae growth with the lids off?

[xtrstangx]

Originally posted by awestruck
Thank you!!! I have 1 T5, and 2 pc's. I have seen the legs at my LFS and that sounds like the best solution. I like the look of canopies but have no clue as to how to build one so again, the legs are probably my best bet. However, if there is no lid on the tank, do you need to top off more frequently due to evaportation? And, I don't have a real serious problem with algae but could there be a possible decrease in algae growth with the lids off?

You may have a bit more evaporation, it won't be a huge difference.

You may get a higher pH without the lids that may help lessen the algae, but I wouldn't count on it.

[InsaneClownFish]

I sit my T5 fixture right on my glass top. As xtrs has said, no lid is better for gas exchange, and you will evaporate water alot more quickly.

There is nothing wrong with a glass cover as long as you have sufficient cut outs along the back...there needs to be some openings! Also, any extra surface aggitation will help...

Also be mindful that you need to keep an eye on any MACRO algae...this may seem strange but macros can strip the water very quickly of dissolved oxygen...if you have too much it will rob your corals....

[awestruck]

Ok, I have some macro algae in the tank, but not a lot (maybe one average size handful). Further, there is space at the rear end of the tank which is open so some air is meeting with the moving water. However, it sounds as if A LOT of open surface space is better than "just a little". You know, I have a master's degree (not in marine biology) but when I get in some of these forums I often feel like my brain doesn't work very well!

[awestruck]

It's after midnight where I live and it's time for sleep. Thanx for all the help and if anyone can add anything else (a response to my last question/comment) please do so. Peace.

[AD91158]

If your runing a sump and skimmer oxygen exchange is not as important. A skimmer can be viewed as an airston on steroids. A skimmer constantly oxygenates the water as well as removes organics. Therefor it makes no difference whether or not you cover your tank. Of course there are other things to consider like the increased evaporation rate you wil see as well as higher temperatures from heat being traped by the cover.

[InsaneClownFish]

AD ...good points as well...

Just remember that there is a big difference between bubbles from agitation and actual oxygenation. If you have an open sump a cover is almost a non issue with regards to oxygenation.

There is no substitute for surface area though..

My tank is completely covered with cut outs...no sump. If anyone is curious the cut outs are 5 1inch by aprox 2 inch openings....aproximately 10 square inches I would say over the whole...4 maxijet 900s hittin the surface in a 40 breeder...the only time I had issues is when Caulerpa Racemosa went asexual in my tank about 40 times over...now that is an oxygen junkie!

[awestruck]

Hey, I'm back. Thanx for all the help. Yes, I am running a protein skimmer and I have a small sump under the tank but it's closed so it's not helping regarding gas exchange. As I said earlier, there is about a 1" opening at the back so I'm assuming some exchange is occurring. The 58 is doing well--I'm guessing oxygen exchange (or lack thereof) isn't too severe negatively speaking. Then again, the oceans do not have any covers at all! Other than oxygen readers (?), are there any signs that indicate a tank is not exchanging enough gasses? Additionally, my other real concern continues to be trying to get my nitrates to 0. They tend to hang at about 20 which isn't good. Someone named Sk8r advised adding another 1"-2" of sand to my bed (it's now about 2-2 1/2"), and eliminate the sponge in the canister. He advised adding the sand SLOWLY, which is exactly what I'm going to do. You know, hindsight is always 20/20 when some people first start new reef tanks. If I could start over, well darn it, I surely would do it very, very differently. Thanx again for your help, and if you have any more thoughts please share them! and as always, peace.

[awestruck]

By the way, xtrstangx, your avatar is absolutely stunning. May I ask what it is? Once again, I am awestruck.

[Randy Holmes-Farley]

FWIW, carbon dioxide exchange is actually a lot harder than oxygen equilibration (incomplete CO2 equilibration is, in fact, the only reason that pH swings day to night in reef aquaria), but issues around O2 are discussed here:

The Need to Breathe, Part 3: Real Tanks and Real Importance
http://reefkeeping.com/issues/2005-08/eb/index.php

[awestruck]

To Dr. (Mr.?) Holmes-Farley:
Thank you for guiding me to Dr. (Mr.?) Borneman's excellent research article regarding oxygen levels in various tanks with a plethora of variables. I was surprised to see that oxygen levels drop as much as they do once lights go off (natural or otherwise).
One of my questions was answered when Dr. Borneman discussed the clown coming to the top, under the skimmer, for oxygen. This makes me wonder: as fish quiet down and sleep, do they need less oxygen? If not, would it be logical to surmise that fish should, would, or do move closer to the surface as darkness approaches? Furthermore, in addition to mimicking the ocean with similar salinity and temperature in our aquariums, how drastic is the decline in oxygen with, say, a 2 degree change in temperature and a, say, .02 change in salinity (I'm referring to specific gravity read on a hydrometer). This probably is not the place to be asking these questions, but it is interesting and significant to the well being of our aquariums. Thank you for your time and your expertise.

[Randy Holmes-Farley]

This makes me wonder: as fish quiet down and sleep, do they need less oxygen?

They likely need less, but that doesn't necessarily mean that they are comfortable in lower O2 environments when less active. It don't really know the answer.

Both salinity and temperature do impact O2, and those parameters can influence fish in many ways that include O2.

FWIW, I'm not convinced that the O2 levels are really as low as Eric claims in some of the experiments, and I discussed it with him here:
http://reefcentral.com/forums/showth...hreadid=647487

[awestruck]

Thank you Dr. Holmes-Farley for your comments. My comprehension of chemistry is limited thus I appreciate your "easy to understand" responses. As always, peace.

[Jonnyacrofeed]

so does having a powerhead pointed at the surface oxygenate the water or not?

[awestruck]

From what the Dr.s are saying, yes, the powerhead will help because it's moving the water at the surface; and, you will get an even higher exchange (desirable) if lids are absent. Please don't shoot me if I'm wrong.

[xtrstangx]

Originally posted by awestruck
By the way, xtrstangx, your avatar is absolutely stunning. May I ask what it is? Once again, I am awestruck.

Its a Rose Bubble Tip Anemone. Its a picture from my 40g. Unfortunately he died during the transfer to my 180g (my only loss, however the biggest). Thanks for the compliments


RIP

[awestruck]

I have only seen one Rose Bubble Tip Anemone and it was just a baby. It certainly wasn't as glorious as yours was. I'm sorry you lost it. I've lost some too that I loved...

[awestruck]

Apologies for backing up a bit but I have a thought regarding Dr. Borneman's research (oxygen levels w/different variables)--okay, I read that oceans are super oxygenated (which I presume means over 100%.) So, although ocean life may be less comfortable with a decline in oxygen levels as light intensity reduces, perhaps it is still "pretty" comfortable (ambiguous, I know) because the oxygen levels at night may be at the 98%-100% level, and well, 100% is 100%. Is there a positive correlation between slowing metabolism and reduction in need for oxygen (I'm going on the assumption that metabolism slows as ocean life rests/sleeps)? I ask these questions because of the clown that put itself up under the protein skimmer. I mean, I cannot envision ALL ocean creatures moving up in the water as oxygen levels decrease--and obviously, that would be quite the feat for immobile invertabrates--duh. Because of the aforementioned am I wrong in concluding that for aquariums to really do well the oxygen levels should be super saturated during light hours so that as lighting intensity declines the 02 level is still at around 98%-100%? If so, I feel quite challenged in achieving this goal. If this response/question is too long and/or too wordy, thus inappropriate for this forum, please let me know. I'm unsure as to the etiquette expected here. And as always, peace.