Proper oxygen levels???

catfishguy3 · Post by **catfishguy3** » 11 Dec 2007, 19:53

OK folks, I've been keeping fishies since the mid 80's and I confess, I don't test ANYTHING. Many if not most of my fish live for many years and I still have 3 of my original "cats". I guess I've just been lucky. I do heavy water changes weekly, (usually) at least 50%, and clean my aqua clear sponges at the same time, so maybe good maintainance has gotten me by. Having said that, I'm trying to become a better fishkeeper in my old age and I want to begin testing things like desolved oxygen, particularly since I keep quite a few cats, both African and S.American. I run 8-10 turnover rates in all my tanks with Aqua Clear HOB's and keep live plants also, but I honestly don't know what my oxygen levels should be, or what my Ph,Gh or Kh is. I've always believed that if I keep my fish clean, warm and well fed, they'll be fine and such has usually been the case.......Any thoughts, aside from calling me a lazy, so-and-so:)

Dave Rinaldo · Post by **Dave Rinaldo** » 11 Dec 2007, 20:01

Maybe this will help.

From Shane's World

A catfish keepers guide to dissolved oxygen

apistomaster · Post by **apistomaster** » 11 Dec 2007, 20:13

I would be leery of the test results from the chemical test kits. I think they aren't as accurate as one might wish and the electronic DO meters are very expensive.
Staying mindful of the factors that affect DO as outlined in Shane's article is probably the most practical approach.

catfishguy3 · Post by **catfishguy3** » 11 Dec 2007, 20:37

I do agree about test kit accuracy, although since I don't use them my skepticism may be unfounded. I'm an electronics tech, by trade, 30+ years, so accuracy in testing is something I expect, at work anyway. In my early years as an aquarist I tested everything faithfully...and drove myself crazy because there always seemed to be some parameter that wasn't where I thought it should be. The end result of all my testing and tinkering was a lot of dead fish. Since then I concentrate on changing my water and cleaning my filters faithfully and that makes life simpler for me and my fish are generally quite healthy. I'm on well water, so no chemicals to worry about. The last time I checked was 10+ years ago, my Ph at the time was in the low 7's and my hardness was on the mild side. I use HOB filters with sponges only.

apistomaster · Post by **apistomaster** » 12 Dec 2007, 17:35

The difference between the theoretical maximum DO content at 28C/83.4F is 7.8% and at 30C/86F is 7.5%
I don't know if the chemical DO tests are capable of precision to 0.1 %.

Seems easier to minimize factors that reduce DO and maximize factors that encourage higher DO levels and just assume you are doing the best you can at a given temperature.

grokefish · Post by **grokefish** » 12 Dec 2007, 19:24

In my opinion testing water as a hobbyist is a waste of time. I believe it has it's place but not on a regular basis only when something goes wrong. You have been doing alright for a good while now so why change anything?
Ha!Ha! I hope I get a good slating for that comment.
Matt

Bas Pels · Post by **Bas Pels** » 12 Dec 2007, 20:12

I can only agree with Matt, especially whn testing dissolved gasses.

Imagine pouring precisely 5 ml of water, through air, adding some coloring stuff and shaking

The result might tell you exactly how much oxygen, or carbondioxid, is dissolved in the measured tube. Still, this amount had nothing to do with the amount you seek, because the gasses measured have had ample opportunity to escape, or enter, the water.

I do have, however a redox measuring device. This apparatus can be held with its sensitive parts submerged in the tank, and it tells me about the equilibrium between oxidising matter (such as oxygen) and oxygen consuming matter (such as organic waste)

Tapwater maesures over 300, but I once measured less than 0(thus all dissolved oxygen was accounted for). Still, the fish were visibly not happy, so I did not need to measure the water, I knew I had to change water.

I used the meter because I did not understand what was wrong: fish in trouble, but the pump functioning. BTW, no fishes died

catfishguy3 · Post by **catfishguy3** » 12 Dec 2007, 20:24

OK folks, ya talked me into to it...or should I say OUT of it. Good points about test kits and about my current "system" working well for a long time.....If it ain't broke why should I fix it?? Thanks for your input..........

racoll · Post by **racoll** » 12 Dec 2007, 20:39

Ha!Ha! I hope I get a good slating for that comment.

Not from me. I do the same. I have all the tests, but I only use them when setting up a new tank or if I suspect a problem.

I do sometimes do a nitrate test though to make sure I'm doing enough water changes.

Durlänger · Post by **Durlänger** » 14 Dec 2007, 14:23

Bas Pels wrote:I do have, however a redox measuring device. This apparatus can be held with its sensitive parts submerged in the tank, and it tells me about the equilibrium between oxidising matter (such as oxygen) and oxygen consuming matter (such as organic waste)

Redox measuring devices don`t measur oxygen itself, it mesurs redox pairs like SO3 2- and SO4 2-. But not if one of the redox pair is a gas (oxygen) or solid or water (like H2O and H2O2):!:

Bas Pels · Post by **Bas Pels** » 14 Dec 2007, 19:00

I must admit, although a chemist, I never took the trouble to go deeply into redox meaters.

However, I get a beter reading if I aerate the water, and a bad reading explains why the fish don't seem to be happy.

From a practical point of vies, this is good enough, but from a theoretical point of vies, a large difference can be seen between measuring dissolved oxygen and measuring matter oxidised by this oxygen (such as SO3-- vs SO4--)

Durlänger · Post by **Durlänger** » 15 Dec 2007, 18:41

Bas Pels wrote:From a practical point of vies, this is good enough, but from a theoretical point of vies, a large difference can be seen between measuring dissolved oxygen and measuring matter oxidised by this oxygen (such as SO3-- vs SO4--)

agree