Bioload and co2 questions, (complete setup described)

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Tres

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Jul 12, 2007
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Ok I am contemplating setting up a 55 gallon, and I have some questions hopefully one of you experts can help me with!


I do not want to artificially insert Co2, so I plan on using a heavy bioload. Here is my plan, tell me what you think of it.

PH: Comes out of my tap at 7.0. Most of the tanks I have now are 6.6 before weekly water change, and 6.8 after the change.

There will be no air stone, just *some* surface movement due to a canister filter with bioballs and sponges, including a sponge on the intake. I will probably place the outlet at a low position in the aquarium to limit the surface agitation, assuming the plants are producing enough oxygen to keep the fish alive and well.

Due to the bioload, I intend on doing 50% water changes once per week. This works well in my guppy raising tanks which are very heavily populated, and that's where I got the PH figures noted above from.

Because I raise guppies, I will have seasoned water and filters to start out with, YAY!

The tank will be heavily planted with Amazon swords in the rear, Java Moss in the middle, attached to driftwood, and then 6 inch Corkscrew Valisnera up front, along with duckweed up top.

Everything except the duckweed will enjoy this substrate:
1/4 inch peat covered with...
1/4 inch Shultz aquatic plant soil covered with...
1/4 inch eco-complete covered with..
2&1/4 inches small to medium rounded edge gravel.

I may or may not fertilize the water column depending on the health of the plants.

The water will be treated with Blackwater extract (and dechlorinator) in each water change.

For lighting I have 2 3ft long hoods with 2 30w bulbs each on glass lids. That's something like 12 ft of 30w lighting, woot! (4 36inch 30w lifeglow bulbs)

There will be several branch like pieces of driftwood arranged to appear as a mostly covered tree branch, as well as several small pieces of driftwood just laying on the gravel. I am hoping to get the java moss to grow on the driftwood.


I intend to use Malaysian trumpet snails to keep the substrate happy, and then the following fish:
7 discus
20 cardinal tetras
6 Blue rams, 3 male, 3 female
3 True Siamese algae eaters
3 Spotted Corys

I am "hoping" that the snails and duckweed will act as bioload "buffers" if you will, meaning if there is excess co2 the duckweed will increase and if there is excess nutrients the snails will increase, thus increasing the co2, wash rinse repeat type cycle...


My questions fall into 4 main categories...
1) What do you think of the bioload? Could it be increased? Is it too much?

2) What about my idea with the snails / duckweed? Will the duckweed prevent growth of the other plants, even with the substrate described? Will the whole bioload buffer idea pan out at all?

3) Will I be able to keep surface agitation low, allowing most of the co2 / oxygen cycle to be done by the fish and plants? If I am forced to increase surface agitation, will this blow the entire plan up?

4) Am I missing anything major in my plan? Is there an elephant in the room? lol.
 

Star_Rider

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Dec 21, 2005
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Ed
I'm not sure your plan will work..most of the gas exchange happens at the surface of the tank. if you are not adding CO2 you won't be gassing an extra off.(negligable amts)
more important may be knowing what your kH is a neutral ph(7.0) does not indicate your carbonate levels.. if the pH is dropping during the week..I would be more inclined to think it was caused from something other than CO2..
basically CO2 changes the pH by converting the carbonic acid levels..when the CO2 is turned off the pH swings to a normal pH.
if you have a low kH in the water you have less buffering..and this could result in a change of pH.
(in nutshell)
 

Tres

AC Members
Jul 12, 2007
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I think the co2 drop is caused by my less than well cleaned filters, :doh

What adjustments do you think I should make to get something close to this plan working well?

Also, I don't understand something about the gas exchange... what law says it has to occur with surface agitation? I admit to being a newb when it comes to co2, however this is my understanding: Plants suck up co2 and produce oxygen. Fish and snails suck up oxygen and produce co2.
Is there some reason why this can't be the "gas exchange system"?
 

Star_Rider

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Dec 21, 2005
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Ed
there is more surface area exposed to gases in air..that is why there would be more exchange at the surface. (read not all gas exchange occurs at the surface..but a vast majority of it does.)

agitation at the surface increases surface area thus increases exchange.

also keep in mind that when the light goes away plants tend to respire(use O2).

adding an airstone in a tank with no CO2 would not cause any noticable loss and in fact may actually help increase CO2. allowing replacement of any CO2 lost.
 

Notophthalmus

I put the 'snork' in 'snorkeling'!
Mar 4, 2008
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The amount of O2 and CO2 in the atmosphere is much much higher than it will ever be in your tank, no matter what the bioload; this is true in natural bodies of water as well as aquaria. It is definitely to your benefit to encourage gas exchange between tank and atmosphere as much as possible, and surface agitation is the best way to do that (keeping the water a little on the cool side also improves gas solubility).

All plants and animals take in O2 and give off CO2; this is the process of cellular respiration. Healthy plants when exposed to light do not stop respiring, but they give off more O2 than they are taking in and take in more CO2 than they give off. At the macrocosmic scale- the whole Earth, including its water bodies and the atmosphere that connects them all- the system is balanced; there is enough CO2 and O2 given off to balance that taken in. At the microcosmic scale the system is likely to go out of balance very rapidly- if you seal your lovely little aquarium away from the atmosphere, it will quickly turn into a tank of anaerobic sludge.
 

Tres

AC Members
Jul 12, 2007
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Thank you very much for the extremely helpful information!

I suppose the only question that remains is.. assuming I agitate the surface water, and plant heavily, and do 50% weekly water changes weekly, is that too much bio-load for a 55 gallon?
 
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