Hypothesis Insane Pearling on Water Change Day

[Gwad]

Hey all. I remember reading some discussion about this on the Barr Report, but it was all pretty speculative. On water change days, my plants pearl a pretty ludicrous amount. Are you all experiencing similar behavior? I think the moss walls make it particularly noticeable because they grab onto additional bubbles coming from the neighboring plants. They pearl everyday, especially in the last couple hours before lights off, but it is noticeably increased on water change days.





One idea from Barr was that there was extra CO2 coming into the tank from his tap water on change day. In my case, I pump in RO water sitting in a bin in my house, so I would expect that it is closer to the <1 ppm CO2 equilibrium point of water in atmospheric air. Therefore, I don't think that hypothesis was correct.

Anyways, I'm not sure if anyone has an answer, I just wanted to share and discuss if others see this in their tank on water change day.

 

[CincyScaper]

I’ve heard another explanation a few times that I think is a well accepted phenomenon. When we do a water change and the water level drops, the plants are briefly exposed to ambient air. Even submerged aquatic plants can absorb CO₂ from air much more efficiently than from water, so during that short exposure they may load up on CO₂. Once the tank is refilled, that could translate into a burst of photosynthesis and the pearling we often see shortly after. Some even goto the extent of doing the water change during the photoperiod for this reason.

 

[Naturescapes_Rocco]

What @CincyScaper said!

Underwater, we try to get 30-40ppm CO2 in and around our plants.

Our atmosphere is FOUR HUNDRED ppm (and rising ). When exposed to air, these gasses will basically force their way, in some amount, into our plant's tissues.

That sudden burst of CO2 stored in their cells allows for a quick ramp in photosynthesis and oxygen production.

 

[Gwad]

I’ve heard another explanation a few times that I think is a well accepted phenomenon. When we do a water change and the water level drops, the plants are briefly exposed to ambient air. Even submerged aquatic plants can absorb CO₂ from air much more efficiently than from water, so during that short exposure they may load up on CO₂. Once the tank is refilled, that could translate into a burst of photosynthesis and the pearling we often see shortly after. Some even goto the extent of doing the water change during the photoperiod for this reason.

Woah! That makes sense. Thanks guys.

 

[Dennis Wong]

Woah! That makes sense. Thanks guys.

Barr claims that this is the main reason to do water changes before the light window, and why more regular deep water changes are growth boosting.

 

[Koan]

Barr claims

Paging @plantbrain, @plantbrain to the white courtesy telephone please

 

[plantbrain]

Paging @plantbrain, @plantbrain to the white courtesy telephone please

I don’t use land lines,

Aquatic plants when exposed to air absorb far more CO2 because their tissues are like a sponge with lots of air spaces for the root systems., the other reason is their enzyme that foxes CO2 is very high in submersed plants as it’s somewhat to strongly limiting in aquatic conditions. Third all that O2 from the air also gets into the tissues and is pumped into the sediments. This enhances the rhizosphere and Bacteria so lots of CO2 is given off as well as plenty of O2. Healthy vigorous plant growth as Leo does this. That healthy bacteria and root rhizosphere are a potential community control to reduce algae blooms. Bacteria led to Cyanobacteria and that led to algae. Aquatic plants are fairly recent as submersed autotrophes. Adding more O2 from warming water that was sealed in your water heater has higher O2 ppms than most tanks. Quite a few things are going on. Micro bubbles have surface tension that stick and lift off periphyton on plants and surfaces. Water is clearer and cleaner, lastly you can see the water change effects on the glass algae….where your water changes stopped. It’s pretty clear it has a strong anti algae effect. Plants, glass and hardscape etc are cleaner when exposed to air for a few minutes etc. also a good time to add spot treatments of peroxide and then refill right away.

View attachment 15221

 

[Gwad]

Aquatic plants when exposed to air absorb far more CO2 because their tissues are like a sponge with lots of air spaces for the root systems., the other reason is their enzyme that foxes CO2 is very high in submersed plants as it’s somewhat to strongly limiting in aquatic conditions. Third all that O2 from the air also gets into the tissues and is pumped into the sediments.

This is fascinating. Thanks for the in-depth response. I like having a basis for why we do the things we do. My tanks have certainly never looked better than they do after becoming diligent with large weekly water changes.

Do you have any recommended books or other references to learn more about submersed plants at an intermediate level? I'm probably out of my depth but I took 100 level plant biology and a botany lab in college

 

[Rob23]

Those running a sump setup could introduce regular, scheduled low tide events. Would be interesting to see the long-term effects of daily partial drain and fill with the same water.

 

[Naturescapes_Rocco]

ADA made a tank that does this!


See this video at 16:08 for the daily water-level changing system:

 

[plantbrain]

This is fascinating. Thanks for the in-depth response. I like having a basis for why we do the things we do. My tanks have certainly never looked better than they do after becoming diligent with large weekly water changes.

Do you have any recommended books or other references to learn more about submersed plants at an intermediate level? I'm probably out of my depth but I took 100 level plant biology and a botany lab in college

Biology of Vascular Aquatic Plants, an old book by Sculthorpe. He died young and did this book in his 20's.

A lot of things you just have to learn yourself.
Test it, and see. Most hobbyist can tell if something is growing significantly better.
Ruling out the other issues is key however.

If you can do both of those things, then you can figure out a lot.

People often said "oh that's just the colder water degassing, it's just air. "
Well, there's a lot more to it than those dismissive types of comments.

Now could all these water changes also be applied to a non CO2 method for planted tanks?
Guess what? The answer is yes. Very much so.

A pair of sponge filters, air driven on say an 80 liter tank, works really well.
The impact is larger on water change days obviously in both the CO2 and non CO2 approaches. Perhaps a little more so
for the nonCO2 tank. Adding lots of air bubbles to the non CO2 tank, microbubbles and macro bubbles..........hitting the plants, or from a HOB that has a spill lip and air gets pulled under the water......................a certain Sudipta Shaw might find it interesting as it has a lot of explanatory power.

In otherwords, adding a lot of aeration and bubbles might help more than we assume. I've seen it in aquariums, both CO2 and non CO2, and natural systems also.

 

[Koan]

..a certain Sudipta Shaw

Paging @sudiorca

 

[ElleDee]

Now could all these water changes also be applied to a non CO2 method for planted tanks?
Guess what? The answer is yes. Very much so.

A pair of sponge filters, air driven on say an 80 liter tank, works really well.
The impact is larger on water change days obviously in both the CO2 and non CO2 approaches. Perhaps a little more so
for the nonCO2 tank. Adding lots of air bubbles to the non CO2 tank, microbubbles and macro bubbles..........hitting the plants, or from a HOB that has a spill lip and air gets pulled under the water......................a certain Sudipta Shaw might find it interesting as it has a lot of explanatory power.

In otherwords, adding a lot of aeration and bubbles might help more than we assume. I've seen it in aquariums, both CO2 and non CO2, and natural systems also.

Just so I understand what you are suggesting here, the idea is to use bubbles to deliver gases directly to the plant, bypassing the need to diffuse it into the water? Or to increase diffusion with increased surface area and contact time?

I have a surface skimmer on a large non CO2 tank that a run for a few minutes every now and then to clear any film. I usually turn off my filter when I do this because it clears faster (and there are some foods that I prefer to give the fish without flow), but if I ran the filters and the skimmer together it would disperse the bubbles fairly well throughout the tank. It's not a ton of bubbles, but I could still try it out for a few weeks and see what happens. (This tank already gets large weekly water changes.)

 

[plantbrain]

Just so I understand what you are suggesting here, the idea is to use bubbles to deliver gases directly to the plant, bypassing the need to diffuse it into the water? Or to increase diffusion with increased surface area and contact time?

I have a surface skimmer on a large non CO2 tank that a run for a few minutes every now and then to clear any film. I usually turn off my filter when I do this because it clears faster (and there are some foods that I prefer to give the fish without flow), but if I ran the filters and the skimmer together it would disperse the bubbles fairly well throughout the tank. It's not a ton of bubbles, but I could still try it out for a few weeks and see what happens. (This tank already gets large weekly water changes.)

Bubbles to a less degree than the actual water change exposure. But ample bubbles, say from Aeration driven filters, waterfall like spilling, also add O2, not just CO2. You can do a few things here if you want to test,

1. add more CO2 gas
2. add more O2 gas (those O2 electrolysis products are fairly cheap, 30-40$ etc. They add O2 but not too much like many would do, too much O2 is far more lethal than CO2 actually.)
3. add microbubbles
4. add large aeration bubbles
5. Exposure to air for say 5-10-15 minutes etc, or a 1/2 hour (and mist plants so they do not dry out etc)

These are relative easy treatments. If you lack CO2, DIY yeast can do this up to say a 90 Gallon tank with 4 x 2 liter jugs.
O2, those electrolysis units are cheap. O2 meters are not cheap.

Use a pH meter to track changes on CO2 content.
An O2 meter would be a wise idea.
I have 2 so I can measure that parameter.
Track plant growth over at least 8 weeks. Track each species you keep.
You have 5 possible treatments of one variable.

So about 40 weeks if you repeat the test with each variable.
Take the 2 or 3 or 4 or 5 and test together. This will take a long time, hehe..... when you add them in combinations.