Pearling after a water change? Why?

aaronnorth

Member
Joined
19 Feb 2008
Messages
3,953
Location
worksop, nottinghamshire
Me and Dave was having a discussion about why pearling ooccurs after a water change.

Dave's thoughts were that when we do a waterchange, the plants are exposed to an unlimited supply of gaseous CO2, so they go into 'hyperdrive' and produce lots of oxygen which can be seen as pearling.
While I agree with this, I then questioned it because carpeting plants do not have have access to this unlimited supply (like HC/ glosso etc). His reply then was "It may be more pronounced after a water change because the plants that were above the water line are carbon loaded and not taking so much from the water column, making more available to the foreground plants (just sumerising here, Aaron)."

My thoughts were that the water we add to our tanks, is saturated with oxygen, so therefore no more can be dissolved into the water, so any oxygen produced by the plants is seen on the leaf tips. (I suppose this is similar/ different way of explaining "pearling occurs when the rate of production is higher than the rate of absorption")
Dave's reply to this was that if the water was O2 saturated, then we would see oxygen bubbles appearing on the decor, glass and fish etc.

I m not agreeing nor disagreeing on anything said above... but i was wondering if anybody else has any thoughts on why pearling occurs after a waterchange?

Thanks, Aaron
 

GreenNeedle

Member
Joined
19 Jul 2007
Messages
2,720
Location
Lincoln UK
I would sway more to the oxygen side because after water changes all my glass pipes and drop checkers and diffuser are covered in the bubbles too!!

AC
 

altaaffe

Member
Joined
13 Jul 2008
Messages
309
Location
Thornhill, Egremont, Cumbria
SuperColey1 said:
I would sway more to the oxygen side because after water changes all my glass pipes and drop checkers and diffuser are covered in the bubbles too!!

AC
I'd agree with that too, I get bubbles along the glass where the water line was sitting during the water change too.
 

Superman

Member
Joined
29 Jan 2008
Messages
1,804
Location
Cheltenham
I would of thought along that the water is saturated with O2 after the water change. Although, I do get this fake pearling before I add new water sometimes.
 

Ed Seeley

Member
Joined
3 Jul 2007
Messages
3,261
Location
Nottingham
I'd agree it's the extra oxygen in the new water that lead to more prevalent pearling. I think Clark means it's fake pearling in that it doesn't rely on oxygen produced by the plants to create the pearling but the oxygen present in the new water. After all after a large water change you can get oxygen bubbles over the hardscape too after a big change.
 

Superman

Member
Joined
29 Jan 2008
Messages
1,804
Location
Cheltenham
I generally class it as fake pearling as its down to what I'm doing to the tank, rather than the tank doing it for me.
 

GreenNeedle

Member
Joined
19 Jul 2007
Messages
2,720
Location
Lincoln UK
Ed Seeley said:
I think Clark means it's fake pearling in that it doesn't rely on oxygen produced by the plants to create the pearling but the oxygen present in the new water. After all after a large water change you can get oxygen bubbles over the hardscape too after a big change.
I agree with that totally Ed as per my first post. I was questioning how it would be 'fake' pearling 'pre' water change.

AC
 

Ed Seeley

Member
Joined
3 Jul 2007
Messages
3,261
Location
Nottingham
SuperColey1 said:
Ed Seeley said:
I think Clark means it's fake pearling in that it doesn't rely on oxygen produced by the plants to create the pearling but the oxygen present in the new water. After all after a large water change you can get oxygen bubbles over the hardscape too after a big change.
I agree with that totally Ed as per my first post. I was questioning how it would be 'fake' pearling 'pre' water change.

AC
Didn't catch this bit last time. I agree it should only happen after adding new water unless removing water means that filter returns splash more and cause air bubbles in the water - very different to oxygen saturation.
 

GreenNeedle

Member
Joined
19 Jul 2007
Messages
2,720
Location
Lincoln UK
Mmmm. I'm not as convinced. I see what Tom is saying and it does make sense but like someone else say. If I do a 50% water change then only the top half of the plants are exposed to the air. As you know this would explain my fern plants getting bubbles on them from pearling by Tom's theory BUT (and i never really notice if they have bubbles or not) not plants like Crypts etc that I have below the water change line.

This is something I can easily look for on Friday/Saturday when I do my w/c.

It also doesn't exlpain bubbles on glassware where they are all underneath the water level.

I'll do my water change on Saturday just before lights on to see what happens lower down.

AC
 

GreenNeedle

Member
Joined
19 Jul 2007
Messages
2,720
Location
Lincoln UK
I think to add to my last post a better way of testing would be if on Friday I do a smaller 20% water change where not much of the plantmass will get air. Then see what happens compared to a 50% the next day.

If either of these has bubbles in the lower half though it should prove that whilst CO2 access may be the answer that it isn't through exposure. Maybe when we add the water, the water moves through the air between bucket / hose end and takes the air that is passes through into the tank with it??

Anyways I think I will leave this until I do this little test. A test I can afford. lol Not many of those.

AC
 

Superman

Member
Joined
29 Jan 2008
Messages
1,804
Location
Cheltenham
It was an interesting read.
What does Tom mean by CO2 mist injection? Is that with a ceramic diffuser?
 

altaaffe

Member
Joined
13 Jul 2008
Messages
309
Location
Thornhill, Egremont, Cumbria
I wonder if you were to place a bowl upside down and push it down onto the carpeting plants for a while so that they were effectively emersed for a while, if it would then have the same effect on them ?
 

GreenNeedle

Member
Joined
19 Jul 2007
Messages
2,720
Location
Lincoln UK
What Tom is suggesting by mist injection is like when the ceramic diffuser is freshly cleaned and the bubbles look like smoke/mist.

So when used with the needle wheel powerheads or mazzei it chops the microbubbles up into much much finer bubbles.

I don't bother with this anymore as the microbubbles seem to do the job OK as long as circulation is good.

AC
 
Joined
10 Jun 2007
Messages
963
Location
Dorset, UK
I still recon its to do with gases coming out of solution after being pressurised in the pipes, this can take quite a while.. since doing my water changes with 100% rain water I get no hyper pearling at all.

Personally I dont think its anything to do with the plants, I just think its gases coming out of the water, whether thats co2 or o2 I cant be sure of. If you fill a glass with tap water you get bubbles on the sides sometimes.. I recon this is the same thing.
 

altaaffe

Member
Joined
13 Jul 2008
Messages
309
Location
Thornhill, Egremont, Cumbria
I set up my own experiment this afternoon to test the theory. I took a 1 litre plastic jug and placed it upside down into the water to basically give my HC the same effect as being exposed to the air during a water change.

The jug was held in place for 10 minutes (I got bored holding it after 10 mins as the weights I was trying to use wouldn't cut it) and then I observed after 15 mins, 20 mins and 30 mins after removal.

Prior to the start, lights have been on for 2 hours CO2 DC is showing light green.
ExperimentStart.jpg


The jug goes in and effectively makes the HC above the water line.
Experimentjugin.jpg


A few seconds after the jug is removed:
Experimentjugremoved.jpg


20 mins after the jug has been removed (at 15 mins I didn't see any noticeable pearling)
Experiment20mins.jpg


30 mins after jug removal - note the patch to the left, no pearling at all
Experiment30mins.jpg


And finally a wider shot, difficult to see the bubbles (sorry) but you can see that the HC either side has no pearling yet whereas there definitely is on the affected patch.
Experimentendshot.jpg


Al
 
Joined
10 Jun 2007
Messages
963
Location
Dorset, UK
thats a cool experiment.. and certainly proves that plants exposed to the air will pearl on re-submersion. When using tap water I used to get 'pearling' on plants that were never exposed to the air though, which is probably more what Im thinking about with my (slightly shakey probably) theory of compressed gases.
 

aaronnorth

Member
Joined
19 Feb 2008
Messages
3,953
Location
worksop, nottinghamshire
That is very interesting atlaafe.

Matt, i am not sure by the pressure in the pipes etc. But what i believe is that the water is O2 saturated, then this comes out of aqueous solution, and into gaseous solution (this then appears as pearling). I sometimes get bubbles on my glass after a water change, so this could still be in the question.

But the exposed to air method introduces 'real' pearling, whereas the O2 saturation is merely O2 from the water.
 

Similar threads

Top