Replacing air used by plants at night? - The Planted Tank Forum
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post #1 of 8 (permalink) Old 08-28-2017, 06:25 PM Thread Starter
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Replacing air used by plants at night?

My high tech/EI planted 50g has been set up 1.5 months. Besides some minor issues, plant growth has been exceptional.

One of the things I'm trying to resolve is fish respiration. When I was running 30ppm, I noticed faster respiration especially in the first half of the day.

Tank has a HW302 filter, also has had a number of supplemental HOB and sponge filters, and now a wavemaker. Basically two or three sources of water agitation, however, the flow of the SunSun is probably 200gph or less with the griggs reactor.

Ive lowered CO2 to 20ppm, but I still notice some agitated breathing in the morning. My thinking is that the large plant mass is stealing ALOT of oxygen at night and the piddly water movement and bubbling is not really compensating.

I need to get serious about aeration. For those of you who are really attuned to your fish and have a large bio mass, what do you do about aeration? Is your filter turning over 10x tank size/hour?

Should I be running 6+ airstones as soon as the lights go off? Do airstones really help any more than a wavemaker at the water line creating alot of movement?

These are keyhole cichlids, probably on the larger side of fish that would be kept in a planted tank, thus its easy to see their respiration. They have never been gasping at the top, but I want the best for them.
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post #2 of 8 (permalink) Old 08-28-2017, 06:40 PM
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... Should I be running 6+ airstones as soon as the lights go off? Do airstones really help any more than a wavemaker at the water line creating alot of movement? ...
Surface agitation is good to have, but pumping air into the water will raise O2 levels the best. You can use a bubble wand instead of 6+ air stones and hide it along the back somewhere and put it on a timer to run at night. This will also help the plants with their nighttime respiration and you may notice increased growth there too. This may also let you to bring CO2 back up to 30ppm range without affecting the fish
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post #3 of 8 (permalink) Old 08-28-2017, 07:19 PM Thread Starter
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Originally Posted by KayakJimW View Post
Surface agitation is good to have, but pumping air into the water will raise O2 levels the best. You can use a bubble wand instead of 6+ air stones and hide it along the back somewhere and put it on a timer to run at night. This will also help the plants with their nighttime respiration and you may notice increased growth there too. This may also let you to bring CO2 back up to 30ppm range without affecting the fish
One of the things I had in there was a 6" bubble wand w/ 30ppm.. and still breathing problems.

I'm of the opinion that my tank needs serious aeration, maybe an 18" or longer bubble wand... or maybe bubble wands aren't as good as air stones?
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post #4 of 8 (permalink) Old 08-28-2017, 07:31 PM
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...was a 6" bubble wand w/ 30ppm.. and still breathing problems...
Yikes. Yeah, try at least doubling it to 12" then... May ultimately need 18", wow.

Like CO2 diffusers, you'll want a decent quality stone/wand that lets out smaller bubbles. Don't want big bubbles that go straight up and pop without O2 dissolving in your water. I wonder if running your air pump to a large ceramic CO2 diffuser would allow better absorption... hmmm

(It's been a while, but IIRC the blue plastic wands give off big bubbles, while the "green brick log looking stone wands" give a finer mist. I think PennPlax made them? had a trapezoidal shape cross section with nipple on one end...)

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post #5 of 8 (permalink) Old 08-28-2017, 07:32 PM
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There is a thread on this somewhere and even a video on youtube. But basically it talks about how if you run an airstone or have some kind of surface agitation while you run your CO2 it can be beneficial. While it is true that this will cause faster loss of CO2 from the water, it also helps keep more oxygen in the water. Remember the two concentrations are mostly independent.

When there is more O2 in the water, the fish can tolerate higher CO2 levels, but you will also need to use more CO2 since you have more surface agitation. I run my airstone even during the day and am still able to get about 25 ppm CO2. I noticed when I switched to this method my fish stopped breathing as hard. This is just my experience.
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post #6 of 8 (permalink) Old 08-28-2017, 09:18 PM Thread Starter
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Yikes. Yeah, try at least doubling it to 12" then... May ultimately need 18", wow.

Like CO2 diffusers, you'll want a decent quality stone/wand that lets out smaller bubbles. Don't want big bubbles that go straight up and pop without O2 dissolving in your water. I wonder if running your air pump to a large ceramic CO2 diffuser would allow better absorption... hmmm

(It's been a while, but IIRC the blue plastic wands give off big bubbles, while the "green brick log looking stone wands" give a finer mist. I think PennPlax made them? had a trapezoidal shape cross section with nipple on one end...)

My new UV filter has a venturi that injects air into the flow. Looks like a fine mist.. but my guess is that I will need something more. The bubble wall was very fragile and broke. I bought an airstone brick, but it has a defect and most air escapes from the end.
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post #7 of 8 (permalink) Old 08-28-2017, 09:32 PM
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Turn off your CO2 earlier...

Never found a large plant mass to "suck" soo much O2 at night to be able to deplete it..as long as CO2 levels weren't too high..

Quote:
See page 6 of Diana Walstad's book: Ecology of the Planted Aquarium.
"Actually, the air probably provides more oxygen consistently to fish than plant photosynthesis. And while it is true that plants also consume oxygen (plants 'breathe' just as humans do), healthy plants give off far more oxygen via photosynthesis than they consume by respiration. Even when plants are not photosynthesizing, such as night, they probably remove much less oxygen than one would expect. This is because they prefer oxygen stored in their tissues rather than take up oxygen from the water.

During photosynthesis, oxygen accumulates rapidly within the plant lacunae, which are huge gas storage areas making up about 70% of the plant's interior. This internal oxygen is used for the plant's respiration both day and night."

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post #8 of 8 (permalink) Old 08-28-2017, 10:04 PM Thread Starter
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CO2 can't be too high. pH reading 7.0, 6.8 later in day with KH=5.

I turned on the venturi on the UV filter and I'm positive I won't have any more air problems. Tank water is filled with microbubble haze. It has adjustable flow up to 250gph, and a constantwhoosh of bubbles. Will probably only run it nights in future once it clears up the tank. Tomorrow morning I'll see how fish are doing.

I'm really impressed with this UV unit. It solves three problems.. 1) More water circulation 2) Clears bad water 3) More air.

Quote:
Originally Posted by jeffkrol View Post
Turn off your CO2 earlier...

Never found a large plant mass to "suck" soo much O2 at night to be able to deplete it..as long as CO2 levels weren't too high..
I just understood what you meant. Co2 off 2 hrs b4 lights out. Maybe i need to sooner.

Last edited by Darkblade48; 08-29-2017 at 09:26 AM. Reason: Please use the edit function for back to back posts
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