CO2 concentration: pH vs. KH

[Milan]

I've never been able to achieve 30 ppm of CO2 in my tank. I have a DIY CO2 with power reactor, which I would assume is working correctly (plenty of CO2, all dissolved), and is running arround the clock. The problem in mind sits in tap water pH and KH not allowing higher concentrations of CO2. Here are the numbers:

Tap water: KH=6; pH=8.0

After CO2 injection: KH=6; pH=7.1

This gives about 18 ppm of CO2.

Now, what should I do? There are two ways ... If I lower the tap water pH by adding acid (ie vinegar), that would kill the KH, and if I up the KH (ie adding baking soda) that would pull the pH up as well. No win, no win situation seemingly, but one of these ways may work, depending on what is influencing CO2 concentration more. pH or KH? I would like to avoid using RO water, if possible.

 

[Purrbox]

The only way to raise your CO2 levels is to either increase the amount of CO2 that you are injecting into your tank or increase the efficiency of your diffuser. Adjusting your KH and PH chemically will cause both to change not just one independantly.

It sounds like you've got good diffusion, so you would probably want to look at increasing the amount of CO2 that you are injecting. What size tank are you dealing with? Depending on the size of your tank, DIY CO2 may prove difficult to produce sufficient levels of CO2. If you tank is small enough it may just be a simple matter of adding another reactor, or increasing the size of your current reactor(s).

Another thing to look at would be to ensure that you aren't accidently gassing off your CO2. Check that the water being returned from you filter isn't splashing and if you are using a bubble stone/wand during the day discontinue it's use. If your filter has a biowheel, give serious consideration to ditching it.

 

[malkore]

Purrbox is correct...you need MORE co2 flowing into the system to raise CO2 levels.

I have a dKh of 9, and I regularly run 30-35ppm of CO2 (pressurized).

What size is the tank?

 

[Milan]

It's a 29g tank. I'm aware of degassing danger. Although I'm using a HOB filter, the surface agitation is minimal (next to nothing) due to a design modification on it. There is no aeration. The reactor on the other hand does not spit any bubbles out, and there is plenty of gas produced, so I would assume everything goes into the water column. I'm not sure what the thruput of it's pump is, but it is a small(est) submersible pump made by Elite.

 

[Purrbox]

A 29Gal should be small enough for DIY CO2 to get you where you want to go. Next question how many and what size reactor(s) do you have running?

 

[malkore]

Agreed, 29gal is doable for DIY. I suspect you just need more/larger CO2 generators. I recommend half gallon to gallon sized juice jugs.
I had the best CO2 levels with two 1 gallon jugs on my 20gallon, with a Hagen ladder.
Space them apart by a week so they don't both die at the same time.

3 cups sugar is about right. still 1/8 tsp yeast.

 

[Milan]

Thanks guys ... I'll try with increasing the generation of CO2 to the point where my reactor can not handle it any more, and of course, keeping an eye on pH. Will see what amount would that be. Currently I'm using a single 1.5lit bottle.

 

[rich311k]

I use 2 2-liter soda bottles on my 36 and I have had no trouble maintaining CO2 levels over 30ppm.