Air Pump Does It Harm Plant Growth?

[diesel21]

Hi folks,

I was wondering as the bubbles help in the exchange of gases does this mean it stopping the plants in my ten gallon from getting enough c02? Could I say have it on for the day then off at night? I have it on full time at the mo... its a Tom silent air bubbles stellar w-20. Also do you need a special valve to turn it off? As I read somewhere that the water comes up the tube and damages the pump. sorry if these are silly questions!

 

[Truck]

are you running CO2 injection?

 

[three-fingers]

It doesn't neccesarly harm plant growth, just slows it as CO2 will becoming even more limiting as a nutrient.

I run an air pump on my main planted tank, but then I prefer slower plant growth on that tank.

If you want you plants to grow faster, you could keep the pump on from when the lights go off till a couple of hours before they go on.
This is a good thing to do because most plants use CO2 during the day and produce oxygen during photosynthesis, but respire the same as use at the same time (turn oxygen into CO2). At night time, they aren't photosynthesising, so the tank will get a build up of CO2, which the airpump would help gas off.

You would need cheap plug timers for the lights and pump, and a small check valve or two (cost about 40p each from the LFS).

None of this is needed, but if you want your plants to get more CO2, and you have an airpump already, you may as well do this.

 

[diesel21]

no i dont have c02 injection.
Ok thats that helps alot, think I might try and cut down the airpump a bit to get the tank a wee bit more lush looking. I have a fertiliser tab from ebay which I have put into the substrate too.

 

[OldMan47]

Without CO2 injection, there will be more CO2 in the water if you are getting a good gas exchange. There is CO2 in the air above the tank just like everywhere else and that will end up in the water. If you have the air pump at least a few cm above the water level of the tank, you need nothing to protect the air pump. If you have the air pump sitting next to the tank, like so many of us do, a one way valve is an excellent idea to prevent siphoning water when the pump goes off.

 

[diesel21]

right well think I will leave the pump on till the weekend and order a wee valve from ebay?Then tinker with the pump on weekend and trial having it off for a few hrs. But I dont think it'll make much difference but tis fun to try and grow the plants

 

[xxBarneyxx]

Yeah as mentioned above unless you are injecting CO2 in some form or another then better surface movement will increase the gas exchange and help get more CO2 into the water. If you do inject CO2 though then you want less gas exchange to stop the CO2 from going out of the water.

 

[three-fingers]

Without CO2 injection, there will be more CO2 in the water if you are getting a good gas exchange. There is CO2 in the air above the tank just like everywhere else and that will end up in the water. If you have the air pump at least a few cm above the water level of the tank, you need nothing to protect the air pump. If you have the air pump sitting next to the tank, like so many of us do, a one way valve is an excellent idea to prevent siphoning water when the pump goes off.

Yeah as mentioned above unless you are injecting CO2 in some form or another then better surface movement will increase the gas exchange and help get more CO2 into the water. If you do inject CO2 though then you want less gas exchange to stop the CO2 from going out of the water.

Nope, using an air pump to increase surface agitation with the aim of providing plants with more CO2 doesn't work I'm afraid.

A couple of years ago I was thinking about this in a chemistry lesson, came to the same conclusion as you two and was puzzled as to why people recommended that air pumps be avoided on planted tanks.

However, since testing my planted water for CO2 with and without the air pump turned on, and later reading Diana Walstad's 'Ecology of the Planted Aquarium' (excellent book, page 100 relates to what we're talking about here), I now think I understand why.

Sterile water in equilibrium with air contains 0.5 mg/l of CO2, but our aquariums (as well as natural ponds and rivers) contain considerably more CO2, for example my heavily stocked 50gal contains around 20 mg/l and my lightly stocked shrimp tank contains around 8 mg/l. I don't inject CO2 into either of these (yet). The CO2 is coming from everything living in the tank, fish, plants, snails and most importantly the bacteria breaking down the plentiful organic material in our tanks.

Increased surface agitation means more CO2 can gas off and the dissolved levels of CO2 will be closer to that of sterile water in equilibrium with air.


So I would suggest the OP stick to my suggestion of running the air pump during the night using a timer, if they want faster plant growth but still want the fish to benefit from an air pump.

 

[OldMan47]

I see what you mean about CO2 being in excess in a filthy tank with a dirty filter. The sources she cites there are not present in a tank that is getting regular water changes and gravel vacs with filter cleanings. The cited source of carbon in excess of equilibrium is caused by decomposition of fish wastes and dead plant materials in the tanks gravel along with not being removed by water changes. What she seems to be saying is that if you let your tank go long enough with no removal mechanisms, the CO2 will build up to near the levels that CO2 injection will give you. Although I do run a typical Walstead type tank, I do water changes more often than she recommends and I have not tried running it completely without a filter yet. My guess is that few people on this forum would be comfortable running a "pure" Walstead type tank because it runs so much against what else we do. By her statements in the location you quoted, the air pump at any time of day would be a terrible choice in terms of CO2.

 

[three-fingers]

I wasn't talking about Walstad-style tanks .

I'm talking about every day aquariums.

My post didn't contain a quote, those are my own words summarising page 100 of the book into a couple of sentences.
She never gave any figures for aquariums - I was talking about my own tanks - and my shrimp tank gets a 50-60% water change weekly.
My 50gal even has an air pump running on it - but this is because it's a corner tank with a low surface area compared to other tanks and it has a very heavy fish load with some big messy fish. I do 20% water changes on it every 2-4 weeks, and I really don't want my plants to grow any faster as I'm too lazy to take them out.

Test your aquariums - even the bare-bottomed ones that get 100% water changes weekly will have more than 0.5 mg/l of CO2 (not that our test kits are that accurate anyway), sometimes maybe not if they are filtered with air powered sponge filters, have an air stone in them or the filter outlet is above the water - but even rivers and streams in nature have more than 0.5 mg/l of CO2 .

Air pumps should be avoided on all planted tanks if you want the plants to grow faster.

With the exception maybe of people who don't mind spending money injecting more CO2 to compensate for the decorative bubble walls and the like.

 

[diesel21]

mmm quite some debate here, and some interesting points. I dont mind if my plants are a wee bit slower with the airpump on as I feel the fish enjoy the current and it helps in gas exchange. But I think I will trial reducing the hrs its on just to see if theres a difference either way this has brought up some interesting ideas, facts for when I do finally get a bigger tank many thanks for your contributions

 

[Truck]

if you think about it three fingers is right because what respires in a tank:

fish
plants
bacteria
inverts etc