cunniculus

Hi,
I'm new to this forum and to CO2 setups for planted aquaria.

Here's my setup:
-120g aquarium (24" wide)
-Coralife PCs (4x65W) - 12hr. cycle
-Pressurized CO2 tank/Milwaukee pH controller/AquaMedic 500 CO2 reactor
-Small Rio powerhead pumped into reactor to move CO2 bubbles

The CO2 has been set up and running for 5 days. I've managed to drop the CO2 from 7.9 to 7.2 in that time but it hovers there and won't drop. I'd like to see it drop at least to 6.9-7.0.

The bubble rate is very high. I have tried speeding up and slowing down flow through the reactor to increase/decrease the time each bubble spends in the reactor. I know the CO2 is diffusing into the aquarium because I can see the bubbles getting smaller.

What should I do next? Is the reactor too small? It's rated for large aquariums. Should I speed up/slow down the rate at which the water flows through the reactor?

Any help would be greatly appreciated. thanks!

trenac

Welcome to APC

Why do you want to drop your PH?

If you take your PH & Kh you can find the exact amount of C02 in your water... Measuring CO2 levels in a Planted Tank

cunniculus

THanks for the link Trena. I see the logic behind the last paragraph and now feel I should measure the pH. I was under the impression (as a newbie) that I should adjust the pH to a slightly acidic level to promote good plant growth. I guess that's not enough.

Assuming I get a KH test kit and know the pH, how do I know what a good pH level is for the tank?

thanks again

trenac

Plants grow good in a wide range of PH, your PH is just fine for growing them. To get good plant growth you will need the proper lighting for the plants you have, along with a consistent fertilization routine. C02 is also enviable to plant growth.

K20A2

Unless you absolutely need to get the PH down, like for keeping or breeding certain fish, where it’s at now is good. I grow plants fine in a 7.4 PH in my tank.

I did recently set up a 29G and intentionally used peat moss in my filter and a lot of driftwood to leach tannins into the water. The result- a lower KH, GH and my PH dropping below 7. The water is stained now though, like a brown tea.

Rex Grigg

To get 30 ppm of CO2 you should shoot for a 1° drop in the pH.

Also I'm fairly certain that your reactor is NOT rated for a 120 gallon tank. And even if it is then a "small power head" is not going to give you enough water movement to actually move the CO2 rich water around the tank. The best way to dissolve CO2 into the water column is a DIY PVC reactor plumbed into the output line of a canister filter.

hoppycalif

If you want the CO2 concentration to be the same all over the tank, probably an impossible goal, you need good water circulation all over the tank. Remember, CO2 is being used up by the plants and is being dissipated to the air above the tank, so a lot is happening that tends to make the distribution uneven around the tank. Plants inhibit water circulation. So, if you have really good CO2 ppm the plants grow rapidly, and that growth slows the water circulation, causing uneven CO2 distribution. All of that to say, don't rely on a weak filter return or a too small powerhead to do all of the circulating and do it well. Either use a good sized cannister filter, with the output flow carefully watched so it doesn't drop off, or add a powerhead to supplement the circulation in the tank, or do both.

cunniculus

thanks for the notes, guys.

Rex: what do you mean by a 1 degree drop in pH? as pH is a logarithmic measure, there are no units. Do you mean drop from 7.9 to 6.9?

Trena/K20A2, thanks for the pH advice. I'll adjust the controller to shut off at 7.2 or so and see if I can maintain it there.

I hadn't thought about circulation on the level that you guys are recommending. I've got two large powerfilters on the tank but will probably add another powerhead. The small powerhead I mentioned is driving the reactor only (moving bubbles through).

Any other suggestions would be greatly appreciated. it's too soon to see if there any changes. i'm still adding plants.

Rex Grigg

That is correct. If your natural water pH is 7.9 then you want to drop it to 6.9 with CO2.

gibmaker

your ph is fine for growing plants, you should not have any trouble. Although if you have an air stone or a source or sources of oxygen in the tank it is going to deter the amount of co2 being mixed in with the water. The more surface turbulance and constant oxygen the less co2 will readilly dissolve into the water