Pearling after a water change? Why?

[Ed Seeley]

If I understood that correctly you're saying you had bubbles (I'm not going to call it pearling as I don't think it is here!!!!) on the plant leaves while there was no light on in the tank?

If so this is simply O2 coming out of solution as the rise in temperature as the new water warms means the water cannot hold as much O2, becomes saturated and some of the O2 comes out of solution as little bubbles. Are the bubbles on the leaves and the hardscape?

As I said earlier that's not really pearling (where O2 produced by the plants can't get into solution as the boundary layer around the plant leaf is saturated with O2 and no more can dissolve), it's O2 saturated water warming meaning some of the O2 comes out of solution.

Does that make sense?

 

[GreenNeedle]

Not just bubbles. They are quite literally the same as if the lights were on and I did a water change. They are absolutely covered in them. I have just turned the lights on taken a picture and then off again (they would come on in 15 minutes anyway but I am impatient to wait to show this. lol.)

These pics are now 4 hours after the 50% water change and although CO2 has been on for nearly 2 hours this was about the same as it looked (without turning the light on to see) straight after the water change. So no light supplied, definately not pearling, yet the same results as what some are assuming is pearling due to the exposure to air.

There is nothing on the redmoor hardscape but there is (and was) on the glassware, tank seals and Koralia. I guess these are 'stickier' than the wood. lol

Here are the ferns immediately after turning the light on to take the pics:


Some bubbles under the Anubias Barteri


Bubbles gathered under the Lily pipe


Bubbles under the left hand DC (This is the one at the opposite end to the CO2 as I have 2 DCs)


And you can see the bubbles here on the tank sealant/rubber.


AC

 

[Ed Seeley]

So why aren't they "just bubbles"?! I would say that's exactly what they are! The reason they are the same is that the cause is effectively the same - too much O2 in the water for it to go or stay in solution so it forms gaseous bubbles of 02. I don't understand what difference in appearance you are seeing to say they're "not just bubbles"?

These bubbles will form at nucleation sites that can occur on most materials, but obviously your Redmoor wood doesn't have many! You can see the difference easily by doing a little experiment. If you pour some coke (or other fizzy drink) into a glass you get some CO2 bubbles forming but add a soft mint or other sweet with lots of nucleation sites and you'll get a lot more (You may need to do this over a sink BTW). These bubbles are CO2, but the principle is the same.

 

[Dave Spencer]

There is a lot of talk of these bubbles on the hardware being O2. Could they possibly be N2?

As an aside, with my 120cm which has been running for three or four months now, I only get "pearling" bubbles after a water change. With my new 60cm which is about four days old, and getting daily 70% water changes, everything, including hardware that was above the water line is getting covered in bubbles. 🙄

Dave.

 

[GreenNeedle]

I didn't mean 'not just bubbles' as in they are different. lol. I meant that the quantity and positioning was exactly the same as if I were to do a water change during the photoperiod.

I guess all I am thinking is that I don't think it is pearling at all. Wether the plants are exposed or not. I think it's simply O from fresh water that turns into bubbles which of course rise up and get caught under/stick to the leaves/items that let bubbles stick to them. That it's not theplants being exposed that makes them pearl more. Therefore changing 20% water would bring in less O and cause less bubbles than changing 50%.

AC

 

[aaronnorth]

I think it's simply O from fresh water that turns into bubbles which of course rise up and get caught under/stick to the leaves/items that let bubbles stick to them.

That is what my pictures were showing you earlier, it was by no means scientific, but it worked in this case. Also in my cichlid tank i was getting bubbles on the rockwork - no plants in there 😉

 

[Ed Seeley]

There is a lot of talk of these bubbles on the hardware being O2. Could they possibly be N2?

Thinking about it some must surely be air (including Nitrogen) rather than just O2. I'm just not sure about the solubility of Nitrogen in water to be honest!

I think that nay slight rise in the rate of photosynthesis after a water change is probably only a minor factor, I think the bubbles most people see are simply excess gas from the new cold water. However that earlier experiment showed that plants can certainly benefit from the higher levels of CO2 in the atmosphere for a while. Like you though Andy my plants aren't that exposed during water changes. Thinking about it though I haven't noticed lots of bubbles in my tanks any more since I've switched to RO water as my RO water collects in a barrel in the garage and isn't pressurised in pipes before I add it to my tank. It is still colder though - I shall have to be more observant after the next water change!

 

[aaronnorth]

http://www.engineeringtoolbox.com/air-s ... d_639.html

 

[baron von bubba]

just to add my experience of it!
i'm doing 50% changes.
very early on in the tanks life the W/C water added was colder than the tank water, i had lots of this "fake" pearling.
now water added is pretty much exactly the same temp as tank water and i see hardly any of this "fake" pearling after a W/C.

altho the water is sat in a water butt for probably a day longer now than it was at the beginning so that could be another factor or it may actually be the main reason!

if i remember i'll do a W/C that is colder but sat in a butt for a couple of days and the next one where the water is same temp as tank and sat around for a few hours only. guess that would show which is the main reason i dont really see the "fake" pearling that much after a 50% W/C