Dissolved oxygen meter

[Wookii]

How long do the increased DO levels, however they are generated, remain in the water column? With CO2 for example, even with fairly vigorous surface movement from a filter outlet, the levels don’t come down to atmospheric equilibrium even after 12 hours. Is DO similar?

 

[dw1305]

Hi all,

the levels don’t come down to atmospheric equilibrium even after 12 hours. Is DO similar?

Diffusion of all <"dissolved gases is pretty slow">, which is why you need to maximise the gas exchange surface. You can see that this is potentially a two-way street, leading to potential <"oxygen super-saturation in suitable conditions">.

You can process wastes with really high BOD (or you can think of it as <"really large negative ORP values">) if it you can get enough <"oxygen into them">.

cheers Darrel

 

[jaypeecee]

Could an ORP meter be used instead??

Hi @Nick potts

I use a combination of the JBL O2 test kit and an ORP meter. I find that the ORP meter gives a very useful indication of O2 level. As ORP is measuring oxidation-reduction potential, there is not one figure that I could give - all tanks will vary. But, I've done enough measurements now to know what to expect from my tanks. A typical figure would be around +200 mV and I consider +250 mV to be a good reading. I don't use ozone (O3) but measured doses of hydrogen peroxide (H2O2) will, as expected, increase the ORP figure. I still have more experimentation to do. My interest in ORP stems from trying to get a handle on dissolved organics (DOC/DOM).

JPC

 

[Wookii]

Hi All,

Can anyone recommend a decent dissolved oxygen meter for less than £1000. Even cheaper would be better.

Cheers

Stumbled on this whilst looking for dissolved CO2 meters. No idea if it they're accurate enough for your purposes, but Extech models are a bit more budget friendly:

https://www.test-meter.co.uk/catalogsearch/result/?q=dissolved oxygen

Edit: membranes are also a lot cheaper at £25 for 10

 

[dw1305]

Hi all,

No idea if it they're accurate enough for your purposes,

My guess would be that they would do.

cheers Darrel

 

[jaypeecee]

Stumbled on this whilst looking for dissolved CO2 meters. No idea if it they're accurate enough for your purposes, but Extech models are a bit more budget friendly:

https://www.test-meter.co.uk/catalogsearch/result/?q=dissolved oxygen

Edit: membranes are also a lot cheaper at £25 for 10

Hi @Wookii

I have an Extech pH/ORP meter and it has served me very well for over five years. My understanding is that an ORP meter can be converted to a dissolved oxygen meter by use of a semi-permeable PTFE membrane and that's possibly what Extech are using. It's on my 'to do' list! I use the same principle when measuring dissolved CO2 except that I use the pH electrode in KH 4 solution and separated from the tank water by a very thin silicone membrane - it seems to work very well.

JPC

 

[Soilwork]

Stumbled on this whilst looking for dissolved CO2 meters. No idea if it they're accurate enough for your purposes, but Extech models are a bit more budget friendly:

https://www.test-meter.co.uk/catalogsearch/result/?q=dissolved oxygen

Edit: membranes are also a lot cheaper at £25 for 10

i think really I just need something that goes up when there is more dissolved oxygen available and down when there is less. This looks like a good find.

thanks a lot.

 

[dw1305]

Hi all,

I have an Extech pH/ORP meter and it has served me very well for over five years.

This has come my way via my day job, about £500 <"Data Harvest - Wireless Oxygen Dissolved Sensor">. I've no idea how good they are.

cheers Darrel

 

[MichaelJ]

Hi all,

This has come my way via my day job, about £500 <"Data Harvest - Wireless Oxygen Dissolved Sensor">. I've no idea how good they are.

cheers Darrel

Just saw this Milwaukee MW600 on sale. Darrel, what should be the ideal range in a planted aquarium if I may ask?

EDIT: I sometimes wonder about my O2 levels as I have a ton of floating plants in both my tanks - hampering gas exchange I would assume.

Cheers,
Michael

 

[dw1305]

Hi all,

Just saw this Milwaukee MW600 on sale.

I'm sure that would do.

Darrel, what should be the ideal range in a planted aquarium if I may ask?

I like as near fully saturated as possible, but it depends a lot bit on the fish you keep. That is one of the great advantages of planted tanks, they usually maintain higher oxygen levels than non-planted ones (because of the <"net oxygen production from photosynthesis">).

Rheophilic fish from cool water (like Salmon (Salmo salar)) have the highest oxygen demands, but out of the fish we are more likely to keep it would probably something like a cool water Chaetostoma spp. <"Chaetostoma joropo • Loricariidae • Cat-eLog"> or a surge zone Lake Tanganyika Cichlid (Tanganicodus irsacae <"https://www.seriouslyfish.com/species/tanganicodus-irsacae/"> etc.)

Most fish from vegetated ponds are more tolerant of low dissolved oxygen levels, and those from peat swamps etc. often have mechanisms for extracting atmospheric oxygen during low oxygen events.

cheers Darrel

 

[MichaelJ]

Hi all,

I'm sure that would do.

I think I might just buy it.

I like as near fully saturated as possible, but it depends a lot bit on the fish you keep. That is one of the great advantages of planted tanks, they usually maintain higher oxygen levels than non-planted ones (because of the <"net oxygen production from photosynthesis">).

Rheophilic fish from cool water (like Salmon (Salmo salar)) have the highest oxygen demands, but out of the fish we are more likely to keep it would probably something like a cool water Chaetostoma spp. <"Chaetostoma joropo • Loricariidae • Cat-eLog"> or a surge zone Lake Tanganyika Cichlid (Tanganicodus irsacae <"https://www.seriouslyfish.com/species/tanganicodus-irsacae/"> etc.)

Most fish from vegetated ponds are more tolerant of low dissolved oxygen levels, and those from peat swamps etc. often have mechanisms for extracting atmospheric oxygen during low oxygen events.

cheers Darrel

Thank you.

EDIT: I sometimes wonder about my O2 levels as I have a ton of floating plants in both my tanks - hampering gas exchange I would assume.

Any thoughts on potentially low O2 levels due to lack of gaseous exchange from too many floating plants?

Cheers,
Michael

 

[Wookii]

Just saw this Milwaukee MW600 on sale. Darrel, what should be the ideal range in a planted aquarium if I may ask?

EDIT: I sometimes wonder about my O2 levels as I have a ton of floating plants in both my tanks - hampering gas exchange I would assume.

Cheers,
Michael

Nice find @MichaelJ thats one of the more reasonably priced ones I’ve seen!

 

[dw1305]

Hi all,

Any thoughts on potentially low O2 levels due to lack of gaseous exchange from too many floating plants?

Yes, definitely a possibility. All the stomata are on the upper leaf surface, so gas exchange is entirely atmospheric.

Cheers Darrel

 

[hypnogogia]

Nice find @MichaelJ thats one of the more reasonably priced ones I’ve seen!

Hanna instruments range between £550 and £5200!

 

[_Maq_]

Any thoughts on potentially low O2 levels due to lack of gaseous exchange from too many floating plants?

This is well documented from natural habitats. Zones beneath dense canopy of floating plants are poor in oxygen and may become uninhabitable for oxygen respiring organisms. It's a known ecological problem with invasive plant species.

 

[_Maq_]

Hanna instruments range between £550 and £5200!

Try Apera

 

[Wookii]

Only issue for me with many of the cheaper ones (including that Milwaukee one @MichaelJ ) is there isn't a datalogging feature. Call me greedy, but I really want to be able to put the meter in the tank see a profile of the DO over a 24 hour period.

I don't quite understand with these meters why adding the ability to record a few hundred 3 digit numbers results in a tripling of the price!

 

[MichaelJ]

This is well documented from natural habitats. Zones beneath dense canopy of floating plants are poor in oxygen and may become uninhabitable for oxygen respiring organisms. It's a known ecological problem with invasive plant species.

Sure thing. I've actually had constant aeration on my PatMini internal filters (aeration tube connected to the outlet) for a while because of this - not sure how efficient it is though.

Cheers,
Michael