pearling=saturation=myth .. test results

wicked1 said:

My fish have been breathing heavier than usual since I added co2, and my plants have been pearling like mad, so I got a salifert oxygen test kit to see what is going on. (when I added co2 I also removed my sump, so there is definitely less atmospheric oxygen being introduced to the aquarium)

I've been testing a few times a day, every couple of days for about a week now. My results show that the common belief that pearling=oxygen saturation is not true.

I test when I think the o2 should be the lowest - a couple of hours after my air pump goes off, and right after the lights come on. I get a reading of about 7ppm each day. Then I test again in the evening when the lights have been on for 6 or 7 hours and the plants are pearling. I get a reading of 8 to 9ppm. That isn't even 1/2 way up the scale of what the test kit measures! It's actually the lowest recommended oxygen level (according to the test kit literature).

I'm not a chemist (or biologist), so this is just my theory based on what I've observed. I'd say pearling is a result of the plants growing so fast, and pumping out so much oxygen that it forms a large bubble before it even has a chance to completely dissolve.
I should also note that it isn't all of my plants that pearl. It is just the fastest growing plants, but those plants do put off a steady stream of bubbles. Maybe others w/ optimal conditions do reach saturation and have a sea of bubbles in their aquariums as if the entire thing were a huge airstone, I dont know. I just wanted to mention to others who may be trying new things with their aquariums that just because you see bubbles coming off your plants doesn't necessarily mean you have enough o2.

So, does anyone else test for oxygen? if so, could you let me know what your PPM is? I don't want my fish to suffer for the benefit of the plants.

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The difference you are addressing here is the scale, at the leaf surface, there is a thin boundary layer. O2 can and does typically slough off, but it can build up locally.............and does so in natural systems as well........when there is intense fast growth.

So it's really an issue of growth RATE.

Not O2 levels in the tank.

I get about 7ppm ambient and about 9-10ppm during the light cycle.
If you measure a non CO2 tank, you'll have lower O2 levels.

Saturation?
Or % above ambient?

These are two very different conditions.

Regards,
'Tom Barr

wicked1 said:

Thanks!
I think I (and probably others) take some of what we read in forums a little too literally.

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Well, we all do it, I just start questioning it. Coming to some conclusion we can feel confident about is quite another matter though.

Rather than trying to find what it is, try proving that it is not true.
If you can do that, then you can reject that hypothesis and make an alternative hypothesis and try and test that one.
This way you can narrow the choices step by step to investigate down to very few suspects.
Then it's not such an ominous question/process.
But it takes time to do it right, and resources and will.

The biggest lesson to be learned w/ all of this is that each aquarium is different.

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Careful, do not fall for that variability baloney, folks think that there are just too many things to address and give up. That's a quitter's attitude.
Fine if you are a smoker, bad if you want to learn more about the tank and issues:thumbsup:

You cannot test every possible variable here. That's not realistic.
What you can test is a specific condition or treatment.
You can know a lot about that one possible hypothesis/tenatitive reason why.
Example is an old myth that excess PO4 = algae, we add excess to a controlled tank many times to reduce a chance occurrence, results: no algae.
Other's repeat the test, they confirm. This test does not state what causes algae, only what does not under these conditions. We know not to worry about PO4 then and can move on to testing CO2, NH4, light, temp etc from there as to what causes algae blooms.

Do not give up so easily.

What is true for one person isn't necessarily true for everyone.
(and I'm not new to aquariums or forums. It's just a lesson that I keep forgetting)

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Well, understanding why that might be ain't a bad idea to look into then?
Seeing where they went wrong, or where they went right is a good idea.
Something are dead ends and we come back and start over questionign things, murphy's law applies well here.

So do not give up there either.

We all know that plants grow for defined reasons, there is no magic here.
That's a good assumption to work from.

Yes, you keep in mind the variability, but you also keep in mind why/how plants grow and what controls the RATE of growth.

Why do non CO2 planted tanks grow and why do CO2 enriched tank grow well etc? They grow for the same reasons, just 10-20X slower............and that allows different methods of dosing, light, no CO2/CO2 additions, inorganic ferts etc

I've got a little more surface movement in my aquarium, and the fish seem to be doing better. My o2 tests are reading slightly higher, and I guess that little bit made all the difference to the fish.

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Yes, certainly.
Even 2ppm can mean a large difference in fish health, 7 is a good min target, 10 is an upper target.

Do not sacrifice O2 for CO2 additions, you can always add a bit more CO2 easy enough and it's cheap, O2 is critical to fish health though, very hard to bring them back to life! Plants are more tolerant, so error in favor of the fish, then tweak for the plants slowly.