do I need a filter in a planted tank?

[ar0wan]

Ok you gais drew me in
The Airstone vs CO2 debate is missing a variable: CO2 injection

WE AGREE: Airstones create surface agitation which encourages gas exchange

With a CO2 injected tank:
the water contains moar CO2 than the atmosphere
Surface agitation is counter productive as it will gas it off

Without CO2 injection:
plants are still going to use CO2 and deplete the dissolved supply
Surface agitation is desired to pull in CO2 from the atmosphere

Yes I'd run a filter for the circulation and mech filtration

 

[JasonG75]

including hillstream loaches

Your'e going to need A WHOLE lot of current to keep the Hillstream alive. The information is in their name "STREAM" they love fast moving stream, they attach to rocks to hold on.
Don't be surprised to see him belly up, soon

 

[jcardona1]

Ok you gais drew me in
The Airstone vs CO2 debate is missing a variable: CO2 injection

WE AGREE: Airstones create surface agitation which encourages gas exchange

With a CO2 injected tank:
the water contains moar CO2 than the atmosphere
Surface agitation is counter productive as it will gas it off

Without CO2 injection:
plants are still going to use CO2 and deplete the dissolved supply
Surface agitation is desired to pull in CO2 from the atmosphere

Yes I'd run a filter for the circulation and mech filtration

DING-DING-DING

the atmosphere contains co2 somewhere in the 300ppm range. when it reaches equilibrium with a fish tank, it will be about 2-4ppm.

the reason for having surface agitation (surface ripple) when you inject CO2 is to increase the level of dissolved oxygen in the water. That oxygen helps the fish withstand the CO2 you are adding to the water. Oxygen in the water will not adversely affect the plants, as far as I know. That surface ripple does cause more CO2 to be lost from the water surface, but that effect is easy to over ride by increasing the rate of adding CO2 - the bubble rate.

If you aren't injecting CO2, the primary source of CO2 for the plants will be the air. CO2 is extremely soluble in water compared to oxygen and nitrogen. So, water exposed to air will fairly quickly reach an equilibrium concentration, where CO2 is absorbed from the air and lost to the air at the same rate. Exactly what that equilibrium concentration is, I'm not sure, but some people believe it is about 3 ppm. The more water surface area is in contact with the air, the faster the equilibrium is reached, so water ripple or agitation can only help maintain the CO2 in the water.

If you use the Walstad method, using biologically active substrate, the decomposition of organic materials in the substrate adds CO2 to the water, more CO2 than is obtained from the air. (I believe Ms Walstad has demonstrated this to be true). With that method surface agitation isn't a good idea, since there is no way to increase the addition of CO2 from the substrate to make up for the added loss from the water surface.

Surface rippling is good with injected CO2, good with inert substrates, and bad with biologically active substrates.

 

[jcardona1]

And about co2 levels in natural bodies of water:

In nature, the concentration of CO2 is often larger in water than in air but in spite of that the actual availability to the aquatic plant is lower. This is because of the slow movement of gasses in water where the diffusion is 10,000 times lower in water than in air. Hence, although the concentration of CO2 in many streams and rivers may be larger than in air, the slow movement of gasses in water eventually leads to CO2 limitation of aquatic plant growth.

http://www.tropica.com/advising/technical-articles/biology-of-aquatic-plants/co2-and-light.aspx

 

[Sab_Fan]

two of the sharper minds have weighed in here, but you seem to be making different statements (?)

ar0wan says: Without CO2 injection ... Surface agitation is desired to pull in CO2 from the atmosphere

jcardona1 quotes: Surface rippling is good with injected CO2

I go low-tech -- no CO2 injection -- and the expert advice I've seen has always been to avoid surface agitation in such a situation ...

 

[jcardona1]

two of the sharper minds have weighed in here, but you seem to be making different statements (?)

We're actually saying the same things

Without CO2 injection:
plants are still going to use CO2 and deplete the dissolved supply
Surface agitation is desired to pull in CO2 from the atmosphere

is the same as:

If you aren't injecting CO2...water exposed to air will fairly quickly reach an equilibrium concentration...The more water surface area is in contact with the air, the faster the equilibrium is reached, so water ripple or agitation can only help maintain the CO2 in the water.

 

[Sab_Fan]

I edited my post slightly ...

but my main concern was that most advice I've seen -- at least from old school aquarists -- is to avoid agitation in the low-tech planted tank ...

guess I'll do some follow-up research

 

[jcardona1]

two of the sharper minds have weighed in here, but you seem to be making different statements (?)

ar0wan says: Without CO2 injection ... Surface agitation is desired to pull in CO2 from the atmosphere

jcardona1 quotes: Surface rippling is good with injected CO2

I go low-tech -- no CO2 injection -- and the expert advice I've seen has always been to avoid surface agitation in such a situation ...

Ah you edited your posts! The information I posted discussed co2 and non-co2 tanks. For co2 tanks, you do want a ripple, as this promotes oxygen exchange, which leads to the fish being able to withstand higher levels of co2. BUT, you do not want splashing water, as you would have with a HOB filter or an airstone.

In a non-co2 tank, you DO want the suface agitation, as this promotes the exchange at the surface of the water, allowing co2 to enter the water and reach equilibrium with the atmosphere...

 

[ar0wan]

yes we did have opposite opinions on the injected tanks
surface agitation WILL gas off CO2 (as well as oxygenate)

I said to avoid it so you minimize gas off
j sais to just increase bubble count

6 vs 1/2 doz amirite

..In a non-co2 tank, you DO want the suface agitation, as this promotes the exchange at the surface of the water, allowing co2 to enter the water and reach equilibrium with the atmosphere...

This is really the take-away from the discussion

 

[Sab_Fan]

fair enough ... I'll put that in my "something to think about" folder