oxygen testing

having a bit of a mooch around the lfs today, I ended up buying an oxygen testing kit, just out of curiosity more than anything else.

Do any of you use these? If not, it's basically a vial that yo fill with tank water, then add three reagents and measure the result against a colour chart.

I tested my tropical tank about 20 minutes after a good size water change. For the temperature of the tank water (25c) I should have a reading of 8.3mg/l to give me 100% saturation.

Mine measured somewhere between 2 and 5mg/l even though I have two filters causing a decent amount of water surface disturbance - or so I thought!! I put the air bubbles on, left it for about half an hour and retested, and got 8mg/l, so more or less what it should be.

What I am wondering now is - how low does the O2 get to in the night when the pants do their thing and use up oxygen from the tank, and do I need to leave the bubbler on 24hrs a day??

I am sorry I bought the damn thing now - I wasnt worried about the oxygen before

I leave my bubbles on 24/7 in both fry tanks. The one on the 180L is a venturi so no air pump is needed. It's just a little attachment that goes on the filter outlet with a 'periscope' type tube sticking just above the water line. Very good invention & was only about £3 for the juwel one.

I'd try testing the o2 again later, do what you normally do regarding bubbles & lights & see how low it plummets

I usually have the bubbles on for a few hours in the night, but switch it off to give the fish a bit of a break from it and to cut out the noise when I go to bed.

I am just going to test the goldies tank before I do the water change to see how that fairs.

I have never thought about the oxygen levels in the tanks, I always thought the filters did enough, but perhaps not!

well the o2 levels in the goldie tank is fine (pre water change and with no bubbles on), so it only seems to be a problem in the trops tank - which is also the tank where the plants are not doing so well either.

The water temp is just 1oC cooler in the goldies tank (24c), would that be enough to ake such a difference with oxygen consumption?

I am going to turn the bubbles off in the trops for a couple of hours and then see what reading I get. I have got a venturi attachment somewhere, I will have to see if I can find it and perhaps leave it on for tonight.

Ooh sounds exciting. Another test kit to fiddle about with. :lol:

I have good surface turbulence and also have the air pumps on for 2 hours in the evening and I just add Seachem Excel twice a week so no depletion from excess CO2. Think I'll have to get the kit just to double check though.

Mary wrote:

Ooh sounds exciting. Another test kit to fiddle about with. :lol:

I have good surface turbulence and also have the air pumps on for 2 hours in the evening and I just add Seachem Excel twice a week so no depletion from excess CO2. Think I'll have to get the kit just to double check though.

Mary, that's what I have been doing too. The main filter actually causes bubbles to form on the surface while the smaller one causes a wave too so I would have thought that there was enough going on. I have just tested the oxygen level again, after about 3 hours without any bubbles on and the level has gone down to between 2 and 5 again!!! I am going to put the venturi thingy on and see what difference that makes.

Maybe I won't get the test kit then. Ignorance is bliss and all that...:lol:

Well, just out of curiosity, I went ahead and ordered a Salifert Oxygen test which arrived this morning. Happy to report that all the tanks measured between 8 and 12 mg/L of O2 (minimum recommended level is 8mg/L for FW tanks) with the majority registering about 10mg/L. So at least I know the fish have enough oxygen...I could tell that just by looking at them though! :lol:

You just have to fiddle don't you ? :lol:

I do! Funny thing is, I hated Chemistry in school but I just love fiddling about with the test tubes and bottles. I still test the water once a month just for the hell of it! :lol:

i must admit, i like fiddling with things like that too. I usually shout Connor & he shakes the nA test for a minute to save me gettting arm ache :lol:

munchycarrot wrote:

I usually shout Connor & he shakes the nA test for a minute to save me gettting arm ache

That's the only bit I don't like - I've broken several test tubes due to overenthusiastic shaking. :lol: