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Discussion Starter · #1 ·
Qoute : Tom Barr aka PlantBrain
""Why water change day seems to grow aquatic plants better
Basic simple question: why do my plants seem to grow better/best the day of the water change?

I do a large water change in the morning right after the lights come on, then late in the day, there is mad pearling and obviously better growth than any other day of the week.
I've measured plant growth to confirm this also. (stem length and biomass).
I've also done back to back water changes over the entire week, once a day, same time.

I've suggest a few hypothesis:

1. CO2 rich tap water. This is supported and suggested in the Optimum Aquarium(1986) from Dupla's Horst and Kipper, often around 20-30ppm ranges.
One can/could test this by allowing the water to sit for a 1-2 days to degas, then change the water.

Results, we still see an increase in growth.......but this is inconclusive.
I agree there is some strong effect here.

2. Temp differences within a sealed hot water heater and cooler tap water degas once released into the aquarium= cool water holds more gas, O2 and CO2 etc. Same issue as above, plenty of gases available to help growth. Test similar and similar results to above #1 as well.

3. Exposure to air. Plant aerenchyma (think a sponge in water and squeezed, and then out of water and squeezed) acts like a sponge and takes up lots of gas/air and then uses that while exposured during the water change. Larger water changes seem to produce this effect.
Test: large water changes by continuous drain and fill methods vs big drain and then refill after exposure. Seems to be plausible. Results suggest the same. You still need to allow and account for the degassing of the tap water also.

4. Indirect O2 addition= > drives bacterial cycling much faster= . indirect impact on plant growth.

5. Gas films. This was discussed by Ole in TAG, vol 23, No#1, pgs 32-39
A physical gill that improves submersed O2/CO2 exchange in some wetland species. If you add enough CO2, then the gas films do not have any difference in growth rates with/without the gas films(see Fig 7). This is similar to exposing the plants to air during the water change.
www.BarrReport.com

End Qoute!!!



i thought i'd add to this and share here, that my water degasses for a whole day now in a big garbage can. water is brought to close to room temperature and i replace 80% of the water in my sump and in my tank.
water is 76 degrees going in, tank is kept at 78/79

there is no extra oxygen as i jsut have a small pump in the garbage can.
water change is done without lights or co2 on but after the water change is done, plants look "better" i think we can all agree to this, no nutrients added, no co2, no lights, but my plants look awesome.

everything is turned on, lights hit and boom bubbles bubbles everywhere.
there is no saturated water for this to be fake pearling. and don't get me wrong my tank is a sodapop tank every day, but this is just madness



its a stupid hypothesis, but i think plants just like clean water too :)
 

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Agreed. It was an interesting read.

I also believe that trace minerals that might be in tap water could also supplement the minerals plants pull from the water column.

And I base this on absolutely nothing.
 

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There was ample post discussion beyond the quote.

As mistergreen suggest....some tap will have more, and some will have less CO2........surface waters will almost all have lower CO2, well waters will generally all have higher CO2 content.

Some might provide a limiting nutrients, other tanks might not have any limitations..........

etc..........

In each case, there is a good chance that the aquarium looks better after wards.

O2 is almost always higher with tap and vat/reservoir water vs tank water unless it's done the latter 1/2 of the light cycle.

The other hypothesis is perhaps O2 demand by the tank water and consistent export of that, leaving more O2 available that would otherwise be used by micro inverts and bacteria to break down organic matter/waste.

Which could explain a lot regarding daily automated water change systems.
I've installed a few and they seem to be without any issues over long long time frames.

The gas film issue could also provide some insight/support into CO2 mist hypothesis.
 

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Discussion Starter · #5 ·
yes there was PLENTY of discussion but as im not a member i couldn't addon.. so i wanted to start the discussion here

and just to add my two cents. i completely agree plants look better.. oxygen? sure believeable
plants exposed to rfesh air also possible!
and maybe they like clean water too free of other stuff plausible as well

maybe its more a combination

but it is pretty apparent like you said tom, plants do like water changes
 

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Children Boogie
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""Why water change day seems to grow aquatic plants better
Another theory could be entirely psychological. There is no evidence to support the quote.
Water changes are more beneficial for your fishes.
 

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Discussion Starter · #7 ·
Another theory could be entirely psychological. There is no evidence to support the quote.
Water changes are more beneficial for your fishes.
if u read further on the barr report. tom states over a month period the growth difference is significant on tanks that had water changes 3-4x per week
vs tanks that had weekly maintenance
 

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Children Boogie
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Like Tom stated, it might be the case for a few but not the rest. This does not make it law.
You might win at a roulette table once but doesn't mean everytime you're at the table, you'd win.
 

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You know what else "pearls" after a water change? My glass, my heater, even my hands if I was rescaping.

And what do you mean by "Looks better"? It might just be that crystal clean water you just added.

I always thought that aquatic plants needed some time before showing an improvement on their health.
 

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Discussion Starter · #11 ·
You know what else "pearls" after a water change? My glass, my heater, even my hands if I was rescaping.

And what do you mean by "Looks better"? It might just be that crystal clean water you just added.

I always thought that aquatic plants needed some time before showing an improvement on their health.
my water is crystal before and after the water change.. i change 80% weekly. my filter pads bi weekly, and i fluff all my plants bi weekly to keep debris off them and into the filter pad
my water comes out almost as clear as when i put it in
 

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You know what else "pearls" after a water change? My glass, my heater, even my hands if I was rescaping.

And what do you mean by "Looks better"? It might just be that crystal clean water you just added.

I always thought that aquatic plants needed some time before showing an improvement on their health.
I think most advanced hobbyists can tell the difference between false pearling and true. The key is not the pearling, but is there real growth differences?
 

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More frequent water changes also helps to keep algae spores at bay.

Every tank I've seen that has an auto water change system is more forgiving and the plants grow like mad.
 

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More frequent water changes also helps to keep algae spores at bay.

Every tank I've seen that has an auto water change system is more forgiving and the plants grow like mad.
With Algae no doubt. If there is one universal 'truth' with all setups is that the water change helps, fish, plants, scape. As long as the plants have what they need to grow the water change is the key.
 

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More frequent water changes also helps to keep algae spores at bay.

Every tank I've seen that has an auto water change system is more forgiving and the plants grow like mad.
I have one client who has about 10% per day done on automation, generally about 1 hour after the lights come on, then doses CO2 and Excel....as a back up.

The Dosing tanks are 2 x 5 gallons and then 2 x 2.5 Gal back ups.
Carbon block for the tap.

This system has run for about 2 years now.

I come about once every 4-6 months and trim the tank. It's never had any algae issues nor was cleaned. Just fed the fish, algae magnet the front glass once every month or so.

Not bad.

I tend to do my water changes large and frequent in the morning maybe 1 hour after the lights come on. Add ferts back right away etc.
Mad pearling later at night.

This pearling is not on the glass, heater or any other equipment/non live material.
I can easily fluff the bubbles off about 1 hour after the water change and they do not come back(these are degassing bubbles due to high pressure and temp).
At higher pressure and lower temp, the CO2 is higher than at ambient.

If you take this tap water and let it sit for a few minutes, warm up and depressurize........ the CO2 and O2 will escape.
Same for the aquarium.

I think perhaps Ole's work with gas films might apply a bit, it would increase the rates. If you doubt that water changes influence growth rates in your aquarium: a simple test: do water changes daily about 1 hour after the lights come on, say 40-50%. Do this for 1-2 weeks and then do do ANY for 1-2 weeks. See what you think. One day may be hard to tell the differences.

O2 meter does not lie as far as plant growth near the end of the day. It's always higher the day of the water change.
Since I do the water change early on, then 6-7 hours later, the O2 reading is taken.........a direct relationship with the tap is not likely, I also have wet/dry filters which should remove some of the excesses/degassing from the tap, leaving mostly only plant growth production left.

7. Bacterial and periphyton films. As these are exposed to air during the water changes, or high rates of micro bubbles and dissolved air/gases etc..........the bubbles will adhere. They will provide these films with brief high levels of O2, increasing respiration. Some of the surface tension will stick and pull off a lot of these films on plant leaves....... leaving a cleaner plant leaf behind. In the next few hours, the leaves will be recolonized again. This reduces the barrier and increases the Flux across the leaf for nutrients and CO2, light etc.

This may tie into the CO2 mist Hypothesis effect, the mist itself may be doing a cleaning action on the plant leaves.
A water change may also do a very similar thing.
 

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I think most advanced hobbyists can tell the difference between false pearling and true. The key is not the pearling, but is there real growth differences?
But the whole issue is HD and others are noticing excessive pearling, more so than normal. I don't think anyone going to dispute the whole algae part.

So what is in the tap water that is causing better growth compare to EI water and Co2 injection? Also keep in mind that everyone's tap water is different, I know I don't notice any difference at all but than again, I have two very small tanks.

Again, the main question is :

What variable are we missing out? If we're providing all of our plant's need, what is missing. Let me know so I can run out and buy it.
 

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Discussion Starter · #18 ·
my tap water isnt special.. i dose fertilizers directly after my water change... but plants definitely grow better that day, and they do pearl significantly more that day vs other days


similarly i also have a wet/dry. so oxygen levels and co2 are kept pretty stable day after day.

i wonder if we drain tank water in a bucket every day, and then fill it back up with the same water if it would have the same effect????
 

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If I may add this : Takashi Amano does a lot of water changes. I have 2 of his books, he does 50%, sometimes 33% water changes in all of his aquariums, but mostly 50% wc each week.

As for myself, I do not do a lot of water changes, I am too lazy. I have a planted 7 gallons, with one 33% wc each 2 months, I do not have algae issues with it.
 

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If I may add this : Takashi Amano does a lot of water changes. I have 2 of his books, he does 50%, sometimes 33% water changes in all of his aquariums, but mostly 50% wc each week.

As for myself, I do not do a lot of water changes, I am too lazy. I have a planted 7 gallons, with one 33% wc each 2 months, I do not have algae issues with it.
Whether it's EI or ADA (Amano) the water change is part of the overall system. Anyone can have a tank free of algae without a water change the point is it's usually a limited system. Regular water changes increase the range of light, plants, scape, etc. It allows more 'mistakes' we all do them. It becomes a more forgiving system.
 
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