CO2/PH and the bacteria colony

[John Edwards]

First off thanks to those whom were kind enough to answer a newbies basic questions on setting up a planted discus tank.

Basic question again.

Here in SE Michigan we have a PH a touch alky. 7.3-7.6. Many local discus breeders (Great Lakes Discus for instance) have good luck in keeping and breeding in water right from the tap. :D

In a tank that uses CO2 for plants. The addition of the CO2 will cause the PH to drop, right ? :confused: As the controllers I have seen all use PH as the means of measuring the CO2 delivery.

So then how do we control the addition of CO2 in an amount benefical to the plants without changing the water chemistry ? :confused:

Also taking into consideration the water used for WC`s.

It would seem that the discus would be swimming in a constantly changing enviroment with the inculsion of CO2, WC`s and the parameters within the tank itself. :alien:

Could someone help me to understand this or provide a link to explain ?

Thanks

[nacra99]

Hi John (er.. i assume it's your real name also rite?)

So far i have never heard of any way to control the addition of CO2 and not change the water chemistry. The only way i can think of is addition of buffers, but this results in not being able to control CO2 injection using pH.

The water out of my tap is a staggering pH 9.4, even after running through RO i get a pH of about 8.5 - 9+ (which i still puzzle over) but i am able to lower the RO pH to 6.4 by injecting CO2. Even with a controller, it is inevitable that the pH will fluctuate a little bit, (My controller keeps the pH range between 6.35 - 6.45) but i don't think such a small fluctuation like this bothers them too much.

The biggest pH fluctuation happens during a water change, where my pH 8.5 water goes into a pH 6.5 tank. But my experience so far is that this has not been too much of a problem. The CO2 will bring the pH down quite fast and within 15 - 30 min, the pH will be back to 6.5.

IMHO, as long as you have a good controller, small and quick pH fluctuations due to regular maintainance should not bother them. If you have fully grown adults and a well planted tank, it is not necesary to do daily w/c's like we do with growouts, so they won't get these pH changes everyday.

CHeers
Marc

[pcsb23]

John,

A bit like Marc explained, just want to pick up on a couple of things. If the tank is used for growouts, I would recommend a bb tank and don't bother with CO2. Stating the obvious maybe but here goes, only use CO2 in a planted tank and only run the CO2 when the lights are on. Plants use CO2 during daylight and give off O2, during night time plants (and fish) use O2 and give off CO2. Going from low ph to high is significantly less stressful than going from high to low. Having said that some people use fluctuating ph to stimulate discus into spawning - so you've been warned :D

Your water as it stands is fine for discus.

[John Edwards]

Thanks for the help folks. The CO2/PH issue was a bit alarming.

Looks like my set-up is going to revolve around the following.

A tank with a depth of no more then 20" or so. Front to back of 24" Length ?? TBD
Florite (sp),
Eheim with double inlets. One drawing from the surface and the other from mid depth,
4 tube lighting T-5,
CO2 with PH monitor,
substrate cable heating.

Look good ?

[Dissident]

Drop the substrate cable. More of a pain than help in the long-run, and the benifits are marginal at best.

Dont forget ferts.
You really cant pick lighting untill you know what size tank you are getting. 3-4Watts/gallon is a good rule if you plan to use CO2.

[diablocanine]

First off thanks to those whom were kind enough to answer a newbies basic questions on setting up a planted discus tank.

Basic question again.

Here in SE Michigan we have a PH a touch alky. 7.3-7.6. Many local discus breeders (Great Lakes Discus for instance) have good luck in keeping and breeding in water right from the tap. :D

In a tank that uses CO2 for plants. The addition of the CO2 will cause the PH to drop, right ? :confused: As the controllers I have seen all use PH as the means of measuring the CO2 delivery.

So then how do we control the addition of CO2 in an amount benefical to the plants without changing the water chemistry ? :confused:

Also taking into consideration the water used for WC`s.

It would seem that the discus would be swimming in a constantly changing enviroment with the inculsion of CO2, WC`s and the parameters within the tank itself. :alien:

Could someone help me to understand this or provide a link to explain ?

Thanks

One way you control the CO2 is through a PH monitor/controller (IMO, the safest/bestest way). The way you determine CO2 saturation is by measuring KH and PH then using a chart like this:
http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm
When using CO2 it is important to realize that fish can survive at different levels of PH as long as that PH is stable. Fish cannot survive if toxic levels of CO2 are present in the water. It is just as important to realize if you have low KH, say around 2, it is quite POSSIBLE to have a PH crash at any time. If for example you have a PH of 7.2 and set your PH controller to 6.8 it could be a recipe for disaster if you are not measuring your KH to calculate your CO2 saturation. Using another example, lets say your PH is 7.0 and your KH is 4.0 and you set your PH controller to 6.2, refering to the above chart, you just killed a tank of fish. Using buffers really complicates this chemistry and actually throws off some test kits to the point of being inaccurate and unreliable. This chemistry is way above my head, I apply KISS here. Knowing the KH of the water you use be it tap or RO without additives, IMO, helps ensure a stable system when injecting CO2. My KH is 4, before, during, and after water changes, never has changed in all the times I have tested it, I can count on it being 4, so I can set my PH monitor/controller and predict the CO2 saturation using the above chart. One caution, always monitor your fish when setting up a planted tank using CO2 injection! Fish breathing hard or gasping at the surface is a sure indicator they are suffocating and something is wrong. The only thing that changes in my water chemistry is PH level due to CO2 injection and TDS due to fertilizers. I have not seen any stress in any of my tanks during water changes, I do 30-50% at least weekly using 100% unheated RO. Sure the cold water pisses off the Discus, but hey they are cichlids, good to keep the tude fit. Wishing all your Discus act like true cichlids and your future expertise in growing plants require mowing the tank weekly so your fish will have somewhere to swim!....DC

[diablocanine]

Oh, John forgot one thing:

GO BUCKEYES!!

[John Edwards]

Thnaks again all,
Eve you Mr. D (even if you are a buckeye fan :antlers:) for all the help.

The effect of KH was one that was floating in the back of my mind. As we have seen you can have a high PH with a low KH (and vise versa) and get yourself in a heap-o-trouble with CO2. The link you were kind enough to provide and the chart(s) within it have kinda all bought this together.

To just go and add CO2 till you arrive at some desired PH without factoring KH is a recepie for distaster.

Thanks again for all the help folks. A little pre planning is going a long way to getting started off on the right foot.