Water changes and pearling- What up?

[2ManyHobbies]

I have some GIANT vallisneria that is very hardy. I usually thin out the plant every 4-6 weeks- literally pull out new plant shoot and toss them. Anyone interested? Most plants in the 12-18” range though I have trimed some that have been over 24”. I am looking for some hardy corkscrew vallisneria or other plants for possible trade.

What is with my water changes? I change 40-50% of my water every week and before I am even finished my plants are pearling like crazy. Before I even add the KNO3, KCl, phosphate, or traces. This usually lasts about 8 hours before things slow down. My specs:

55 gallon
KH=7 GH=7
PH=6.8-7
110 watts CF
Temp=78
pressurized CO2
Maintain nutrients per forum suggestions.

I would like to see pearling all the time. Is pearling necessarily a sign of healthy plant growth? Any suggestions?

[Starry]

The "pearling" as you add the replacement water is just gases coming out of solution. This isn't oxygen given off by your plants. It also shows on the glass, right? It's very pretty though, so enjoy, even if it's fake. There's no way your plants can respong to the new high-CO2 water that quick, and for you to see the results that quick.

I'm personally not a fan of pearling. If you get "real" pearling, it means the plants are producing more oxygen than they can store - that's just a waste. You don't need to see pearling to have healthy plants. It just goes along with high light - high CO2 tanks. Plant growth and appaearance should be your gauge of overall health, not bubbles. Also, some plants are more "prone" to pearling than others. I've never seen pearling from my Limnophila sessiliflora, but very often on Mayaca.

Another place you see pearling, which is common even if your other plants don't pearl, is on broken or damaged leaves or stems. These give off streams of fine bubbles, as they're damaged and can't keep it in. This happens a lot when Crypt leaves start to melt. Unfortunately it happens to me all to often.

[2ManyHobbies]

I am quite sure that it is pearling; as you said the easiest way to observe pearling is on broken leaves and branches. The bubbles from the water do not collect on the glass, the only small bubble present is from the pearling. The bubbles coming from the leaves/stems and too constant and precise to be outgassing of the water. Any other ideas?

[Starry]

So you're saying that your plants respong instantly, within the minute, to the high CO2 conc of your tap water? I mean, it's totally possible to get pearling from replacement water, but as far as I'm aware, not that quickly.

Are you injecting CO2? Why not increase the concentration if you want to see more pearling? You fish will be fine even above 35ppm, and that should be plenty for your plants. At least try to keep your pH at 6.8 instead of 7.



Edit: Another thought - if your replacement water is so high in CO2 that your plants go crazy, then you should also see bubbles of gas coming out of solution.

Also, you might want to try lowering your temp a bit, just 2-3 degrees (now I'm talking Celsius, sorry), it's quite high as it is. Cold water holds more CO2, but that's not necessarily my reason. Just to see what happens. I find that my plants, esp the Limnophila, grow much thinner in warmer water. It sounds like you have good growth though, so maybe not.....

[Starry]

oops, replied to my own post by accident.... it's entirely possible that i might start having a philosophical debate with myself, especially if i stay in studying much longer in this gorgeous weather

[2ManyHobbies]

I did keep the temperature lower before I introduced the cardinals and rummy nose tetras. Fortunately the plants do not appear to be affected by the higher temperature though some thread algae does appear to grow faster. If the tank temperature becomes a problem as we begin to warm up I will probably have to adjust it as needed.

I will keep a lookout for outgassing when I change my water in another week.

[Ranger]

I have a similar occurrence when I do water changes,. BUT I know the water going in is CO2 and fertilizer deficient. It's not just off gassing from the water because I can see the bubble streams coming from old and new stems and leaves.

Starry I'm going to disagree with you slightly and say "real pearling” occurs when the plants produce more O2 then the "water" can store, in other words the water becomes saturated with oxygen . I think this increase in pearling might be related to the dechlorinting solution I use when I change water. Perhaps it slightly reduces the waters ability to maintain diffused O2 in solution so the O2 that wasn't pearling "coming out of solutions" from the plants now is. Just a thought.


My plants generally pearl through out the day but I have noticed the increase after water changes too.

[carpguy]

This came up recently on another board and the answer that made the most sense to me had to do with high O2 levels, but not with outgassing…

I think that when the water is relatively low in O2 the oxygen from the plants diffuses efficiently and unseen into the water column, below the saturation point. When the plants are producing a lot of O2 or when O2 rich changewater is introduced, the plants cross the saturation threshold. They are producing more O2 than the water can hold and we see pearling from the plants (not on the glass). It has to do with the O2 level in the plants and in the water.

Just a guess.

[RTR]

carpguy hit my opinion on the head. For more detail see:

http://www.aaquaria.com/aquasource/pearling.html

Note that I declined to take a stand on that particular question - I put that under "personal opinion". Yes, it is oxygen from the plants, but it is not under the limited conditions of "normal" pearling.

[GulfCstAquarian]

To throw yet another wrench into the equation, consider that a water change may not be adding a particular nutrient that is causing the pearling. The water change may actually be removing an overabundance of a certain mineral/nutrient that is blocking the uptake of needed nutrients.

For example, high levels of Boron or Potassium are known to block Calcium uptake and slow growth and show some typical Ca deficiency symptoms. This was the case for a long time in my tank, and every water change brought vigorous pearling from the plants. No gas bubble on the glass or tubes. Just coming from the fast growing plants.

My theory is that everything the plant needed to grow was there (N-P-K, light, CO2, etc.) but there was too much of a certain element, and when I diluted those levels appreciably, the plants resumed growth.

Any thoughts?

[RTR]

I'm so neurotic about partials I've never faced a build-up of anything in the water or ferts, and also I don't do strong light, high fert additions. But I see no metabolic reason why such inhibition could not occur, especially for particular plants with need for specific Ca/Mg ratios or N/P ratios, etc.

[Mr.Jingles]

This amazing phenomonom that occurs in every planted tank couldnt merely be the coincidental state of health that the plants are in. Surely, not everyone's plants are as healthy as the next, and surely, someone has a much healthier tank than someone else.

lemme finish later...gotta help with cooking

[Starry]

interesting posts.... i wish i had more time to post, but for now all i can say is that i think it's a combination of all of our opinions, so unfortunately there is no easy answer to getting pearling all the time.

too bad i didn't think of the argument about the amt of O2 the water can hold... that's true, but pearling also does relate to released O2. Plants only release _excess_ O2 - they do use it for cellular respiration as well, same as animals. So anything coming out is in a way "lost" or "wasted" (if we don't take into account gained energy/glucose through photosynth.) Of course O2 is always released, but usually it can diffuse out quite nicely, without bubbles. Bubbles tell me that it's an abnormal excess of )2 trying to get out. After all, you don't get pearling on slow-grwing plants that are not particularly healthy, no matter what you do to the water. So it's gotta do with light/CO2/nutrients, blah blah blah, no time to post....

[carpguy]

The main thing to consider is why the water is at the saturation point. The little bit I offered was to account for pearling at water changes and not at other times.

"Normal" pearling happens when booming healthy plants have been releasing their excess O2 until the tank is just fizzy with the stuff. But there is another phenomena that gets mentioned periodically where the mad bubbles happen at the waterchange and not at all or to a lesser degree at other times.

Just as a model (all numbers being fictional) assume that ambient O2 is 5ppm and saturation is 10ppm. In tank A the plants contribute 4ppm excess above ambient. The 02 dissolves directly into the water column at just below saturation. Tank B has better lights, more CO2, steadier ferts etc. and the plants contribute 7ppm above ambient. Both tanks are healthy and successful but Tank B pearls on its own every afternoon and evening while Tank A only pearls at waterchanges when the gas-rich changewater temporarily lifts the ambient O2 to 9ppm -- the plants keep pushing out their 4 but the water is suddenly unable to hold it beyond the saturation threshold and it pearls away.

I'm going to have to give RTR's article a closer look later, but he goes into a lot of the actual chemistry, including non-fictional numbers and offers several different pearling scenarios. As ever, looks like an interesting and informative read.

For now, to bed…

G'night all.

[Aquafreak]

If the theory of "O2 saturation in the column" is true, then how can it be possible that some of my plants are pearling and some are not? If the water column is saturated with O2 then I'd assume anything the plants produce O2 wise whether its fast growing or not would result in pearling or at least some bubbles on the plant (under the leaf/on top of leaf/roots), however only my riccia pearls and the rest do not, I have green hygro in there, a huge bunch of it, and I'd consider that fast growing and it doesn't pearl not even a single air bubble can be found on the whole plant, it may not be as fast growing as riccia but that shows the theory won't hold any water. All my plants pearls after a water change even my glossostigma. At this point after much debate on this done to death subject, I'm leaning towards "nutrient addition/decline" theory from a water change.

[RTR]

O2 production rate under any particular condition is inherent in the particular plant. Excess O2 release is a similar situation - each plant type's "definition" of excess O2 will be different. There is no requirement that all plants produce at the same rate under matched conditions, or that they release excess at comparable O2 production levels.

Riccia versus the highly vascular plants is not an easy comparison - the structuraly more complex plants can move excess O2 away from the production area more easily and in greater quantity.

[Mr.Jingles]

so, I dont really think that plants produce anything more. I just think they provide surface area for the dissolved gasses to accumulate (similar to clouds) and create the pearling effect.

all those pearls are just the new gases, not the produced gases.

[Ranger]

Wow, Great replies guys

Very enjoyable "hypothesizing" I look forward to reading the link that RTR posted further.

One question: Mr Jingles

Are you using any dechlorinating solution when you perform the water changes?

Concerning the role that O2 saturation might play in this, I question if the dechlorinating solution might temporarily lower the level of the oxygen saturation point.

[Mr.Jingles]

yeah, I use dechlor.

[Mr.Jingles]

you mean in a similar way that salt lowers the boiling point of water??? the saturation point gets lowered when dechlor is added?

what physical and or chemical reactions might cause that?