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Why no 02 in a tank


Pop Eye
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I was thinking about my tank... and I was wondering what would cause me to need air stones in my tank..

I have a 90 gallon with an xp3 on it and it is medium planted with plants.. I have a Powerhead on it.. I do keep the filter part underwater for less noise.. however i see lots of peoples tanks that are fine this way......

If I dont add the extra airation my fish are at the top gasping for o2.......

Why is this????

Cuz ive seen lots of peoples tanks that they dont need the airation....

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I'm not sure, I was wondering that while reading your other post.

I have a heavily stocked 90g and I dont' have an airstone. I have 1 AC300 and 1 AC500. Both are modified to not cause much water noise(not much surface aggitation). I"ve never had an O2 problem. I"ve also come home before to find the power went out during the day and the filters didn't restart. After a day of no filters they were all still ok.

How many fish did you have in the tank?

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Gina, I had 2-Xp3's with spray bars on the top on my 125 for 11/2 years with no air stones. And no problems. I have read that what is needed is surface movement. That is why you add air stones cause it makes surface movement of the water and adds O2. I can make up longer spray bars that fit your tank to use with your XP3 if you need them.

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I too was wondering exactly how this occurred, as any tank with decent surface agitation, and that isn't too heavily stocked, shouldn't require air stones. I've personally never used them.

What temp were you running that tank at when this happened?

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Temp 78. water param.. Good.. Fish.. Heavily stocked.. But still seems weird..

Going to pick up some o2 testing stuff.. see if it is o2.. or maybe something else..

Edited by Pop Eye
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I was thinking the same. I've always heard though that it isn't the O2 thats the problem, that's it a buildup of CO2 in the water and the agitation allowed it to escape (which I why I've read you don't ever want airstones in a tank if you're adding CO2 - it defeats the purpose). I'm not too familiar with the XP's at all, but if I were you I'd be adding an AC 300 or 500 to the tank as a backup.

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The oxygen in the water is not absorbed from the air bubbles dispersed from an air stone but it is picked up from the surface water coming into contact with the air above the water. If the top of the water has a scum on it the water surface does not get broken up or if the air above the tank does not get circulated there will be a lack of oxygen available to be absorbed into the aquarium water. The other consideration is that the higher the temperature in the aquarium the lower the amount of oxygen so if you are operating a high temperature aquarium it is much more important to watch the oxygen absorption.

Terry

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With a temp of 78F, and the only sudden change being an overnight failure of a bubble wand, I think it's fairly safe to say that this was caused by inadequate surface agitation for the bio load in that tank, which caused a serious drop in the dissolved oxygen content. Having plants in the tank wouldn't have helped matters either, as they too consume 02 during the night.

A rather difficult pill to swallow no matter how you slice it, and a classic case of why the redundancy of certain equipment in aquariums can be so vitally important.

Once again, so sorry to hear about your fish Gina, and best of luck with your new Discus tank.

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The last time my tank did this it was due to high nitrite. I have a seachem ammonia alert and it never gave me any indication anything was wrong. Usually you'd expect to see an ammonia spike prior to a nitrite spike. The first time it happened all the fish were dead before I checked the water and everything was OK. The next time I noticed the fish breathing heavy I immediately tested the water and found high nitrite. I had to do a lot of water changes to correct the problem. The next day the filter caught up and all was well. Not sure you had the same problem but it sounds very similar. Not sure what caused it . Maybe did a water change too close to cleaning a filter and the bacteria took some time to catch up not sure but I do know that the worst part is not knowing the cause .

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Might as well add my two cents worth as well !

I read an article a few months back about airstones and it stated that they are actually a waste of time the only bennifit is the disturbance of the water surface that may break up the film on the water if there is a film.

I have alway used AC HOB filtres and this seems to look after both of these problems ( surface film and airation ) and I always put double the needed filtration on my tanks , one on each end of the tank... not sure why I started doing this LOL but I have myself conviced now that double filtration is best... I could be out to lunch on this theory..

Is there a possiblity that your filtration shut down over night Gina?

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I was thinking about my tank... and I was wondering what would cause me to need air stones in my tank..

I have a 90 gallon with an xp3 on it and it is medium planted with plants.. I have a Powerhead on it.. I do keep the filter part underwater for less noise.. however i see lots of peoples tanks that are fine this way......

The filter should cause enough agitation to aerate the tank if it is setup properly, but if you had it completely below the surface then this would not happen. This would mean that the only thing causing surface movement would be the air stone. As stated earlier A heavily stocked tank with plants to boot would use a lot of oxygen at night and generate a lot of co2. It is most likely that the output on the filter on it's own was not moving the surface, or not moving enough to keep up to everything else in the tank.

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You might want to have a look at this article... http://www.cichlidforum.com/articles/water_movement.php.

Also, especially depending on your stocking for the tank, an xP3 is not particularly big for a 90 gallon tank. I know its rated for up to a 175 gallon tank, but its listed waterflow on the box is only 187 gph. For comparison, the XP2 is only rated for up to 75 gallons and yet its listed waterflow is 160 gph. :huh: That xP3 is only turning your tank over twice per hour. Most recommendations are for 5-10X hourly, again depending on planting and stocking levels. I'm running an xP2 and an AC 30 on my 21 gallon fry tank and with the long attachment to the spray bar, its barely disturbing the surface. Whether this level of filtration is the source of your problem or not, you may want to think about increasing the filtration.

Good luck with your issue. Keep us posted.

Edited by Albertan
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Again, how about the stocking levels? How heavily stocked was it BEFORE you added thejuvies, and how many of them did you add? Fish sizes?

I'm thinking the combined intro of the juvies with the above factors probably created a snowball effect.

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When I lost a couple of fish one night, almost lost them all, this was the scenario.

I had just done a water change and had overfilled it a little, right up to the top brace. 55 gal.

I usually leave one lid open but my wife closed both of them after feeding.

A rock rolled down and pinched off my airline.

At the time I was running 2 203s with the spray bars under water.

I came downstairs for something at 4 am. the 2 severums had died and the rest of the fish 5-6 were gasping.

I now run one 203 with an ac-300.

We should remember that the water is not only agitated by the HOB, it also is exposed to air as it runs over and through the filter media.

I personally run air in every tank I have, one for peace of mind, the other for the looks the bubbles make.

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