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I'm finally getting some decent co2 into my tank via DIY 1.89 liter bottle.

My KH level has moved down from 3 to 2, and ph is down from 7.0 to 6.6 I guess that would put my co2 at about 18 to 20 ppm.

I'm using the hagen ladder diffusor, but the only problem I see is the bubbles come out in groups of 5 to 8 then there's a pause sometimes for about 6 seconds then another 5 to 8 come out in rapid fire fashion.



My Scapes

I wouldn't worry about it as long as your CO2 level is where you want it. 18-20 mg/L sounds good to me... in other words, "if it ain't broke, don't fix it"

Thanks Gold Digger!

How often do you usually apply ferts. I know it's not that simple, but I'm trying to get some kind of handle on it.

With the co2 levels I described and having plants like wistera, sunset hygro, polysmera. Right now I don't have a way to measure iron levels.


My Scapes

Tetra - how did the kH levels drop?

Hey Cory!

I wanted to find out if that's normal.
I definitely have increased co2 production w/1.89 liter bottle, but as mentioned my kh definitely dropped to 2 from 3 (same test kit).

Right now I have so much stuff going into my water (kno3, ferts, melafix (treating sick Angel), flourish excel I don't know what's affecting what:%)

My Scapes

I think some plants can use up that which makes up kH, but I'm not sure. I need to check mine, which I have not done in a while.

Are you still using the Hagen cannister, or have you made your own bottle?

I made my own 1.9 liter juice bottle and am using the hagen diffusor. Strange think it kicks out 6 to 8 bubbles rapid-fire then for about 6 seconds nothing and then 6 to 8 bubbles.

My Scapes

that IS normal.....KH is often called "buffering capacity" for a reason.

Basically what happens when you add an acidic substance to your tank water is that the buffering ions (which are basic) are "used" (neutralized) by the acidic ions before the acid will actually lower the pH of your water. It is a bit complicated to explain without going into chemical equilibrium and a bunch of really boring concepts and theory, but to make it easier: instead of thinking of your water as one mass, think of it as a mixture of acidic, neutral and basic components.

If your tank water has a neutral pH of 7.0, the acidic, neutral and basic components are all there in equal numbers. If your pH is lower than 7.0, you have more acidic components than basic, if the pH is higher than 7.0 you have more basic components than acidic ones.

All the time in your water, the acidic and basic components are bumping into one another and either combining (bonding) to form salts and water (neutral components) or just bouncing around randomly on their own. Adding more base, acid, or whatever, will affect the pH balance of the whole as the small particles interact with one another.

KH (buffering) pieces are basic components (Carbonate Ions). When you add something acidic (like CO2), the KH particles react with it and neutralize, effectively consuming part of your buffer. This is the same reason why old tanks tend to have pH crashes, and also why you need to use a LOT of pH up/down to cause a permanent change in the pH of your water. Certain waste products are acidic, they use your buffer up and there is nothing to keep the pH from dropping to a very low acid state.

You add "acidic" CO2, it reacts with basic carbonate ions (your KH buffer), and lowers the buffering capacity of your water, and the KH reading you're going to see when you test it.

So, anyway, if you're still reading after that, lowering of buffering capacity or KH is totally normal when you're adding CO2 and is actually to be expected. If you find the KH dropping dangerously low, you can replace it with water changes with regular tap water, or dose with dissolved baking soda.

EDIT: oops missed that....

How do you know how much fertilizer to add?

You don't really, sorry. :%) I just start with the recommended dose on the bottle, then watch my tank for signs that I need to add more, or dose less next time. There are too many factors affecting plant nutrients and no two tanks are exactly alike to give a specific value that will work for everyone.

I already posted some info on this HERE (clicky!) this morning. Check it out.

Last edited by Gold Digger at 13-Apr-2005 10:28

Hi,
Over time the KH will shift, downward, as the plants
use the Carbonate, (primarly the Carbon) as they grow.
You should always check the parameters of your tank at
a regular interval, especially when you are injecting CO2.

When injecting CO2, you should strive to keep your KH
around a 3, minimum. Any lower and the pH swing between
"day" and "night" could easly become excessive and stress
the fish. KH is a buffer to the acid formed by the CO2
and the water. It modifies or neutralizes the acid.

With DIY CO2, you have to balance the KH and the injection
rate (which is not controlable, it is what it is for the
mix that you use, and the temperature you keep it at.)
to obtain a desired CO2 saturation. In this case, were
you to raise your KH back to 3, your pH would shift up
and your saturation would drop.

This is one of the drawbacks of DIY CO2 injection. With a
pressurized system, you simply look at the chart and
decide what pH you want to maintain, and what CO2 saturation
you want to have, then maintain the KH and adjust the
needle valve to provide the desired amount of injection.

Where you are is fine, but watch the pH shift and if it is
too much, you may want to return your KH to 3.

Frank


-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--

Ok....2 posts saying plants will use your buffer....

From a chemistry perspective I think this is a myth really... The addition of acidic products like CO2 has a FAR greater effect on your buffer than plant growth. The amount of carbon used by plants would be negligible in comparison, at least IMO&amp;E anyway. If plants consumed THAT much carbon, we'd all be in a lot of trouble. Our tanks would be crashing all over the place.

In planted tanks that I have without any CO2 injection whatsoever, and fast growing heavy feeding plants like hornwort, etc., my pH is constant at 7.2 and my buffer doesn't MOVE. It doesn't move anywhere. If plants used enough carbon to consume my KH buffer to the extent that the addition of CO2 does, I would expect a shift in pH within a very short amount of time. Might be a nice thought but it just doesn't happen. Beacause of the different plants that are chosen for tanks that recieve no CO2, I really don't have a whole lot of difference in growth between CO2 injected and non-CO2 tanks, so that wouldn't explain it either.

The only tanks that see any drop in buffering capacity are those that have some acidic product being added regularly, usually CO2 and/or peat moss, or whatever else I'm using to drop the pH and hardness in the tank water.

Plants do not lower your buffer, it's adding anything acidic that does it.

Thanks Gold Digger and Frank, both very insightful. A couple of quick questions.

1. I know this has been asked before, but wouldn't it be beneficial to my fish to simply pull the hose out of my bottle at nite, to ward off a ph crash, etc.

2. What's the simpliest way to get kh up if too low.



My Scapes

1. Yes you can do that if you want, lot of DIY CO2 people remove the hose when they shuit the lights out. There are mixed reviews on this, I just leave mine in because I'm lazy....hasn't caused any problems.

2. The easiest way to increase KH is to add dissolved baking soda. The way I do this is to add a small amount at a time, usually 1/4 or 1/2 tsp per 10 gallons of water or so, leave the tank for an hour, come back and test my KH and pH to see if I need to add more. Don't add too much at a time because a large swing in pH can stress your fish. It is easier on them to raise pH than it is to drop it, but swinging in any direction can stress them out so be careful. This method is a bit hit-and-miss but I find it is best to determine the dosage of any additive like this experimentally. A good KH to aim for if you're having pH issues is about 3-4.

Here is a page from the krib that explains pH - KH - CO2 relationships in far greater detail than I care to : [link=LINKY]http://www.thekrib.com/Plants/CO2/kh-ph-co2.html#3" style="COLOR: #FCE7A4[/link]