# how to make a fish safe co2 system?



## dodgefreak8 (Jul 26, 2006)

hey everyone I am wanting to try co2 in my 220 but I just can't get over the safety factor for my $600.00+ worth of fish. I was wondering what equiptment I should look into to make this system as safe as possible. I am already thinking of doubling the solenodes so if one fails the other will catch it. I am also looking into the clippard low pressure regulator from rex grigg to help prevent the end of tank dump. I am also considering just dosing a relativly small amount of co2 to start and seeing how it works. Does anyone have any more advice or experience that can help?
thanks


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## hoppycalif (Apr 7, 2005)

Everything depends on how much light you have. If it is a lot, the need for CO2 increases, and failing to meet that need means lots of algae. But, if the light level is low, and the plants don't need more light, you can go with low CO2 and no problems. Even a cheap regulator, like my Milwaukee combo unit, along with a needle valve used to control the flow, will prevent really bad end of tank dumps, and for more insurance you can refill the CO2 tank as soon as the tank pressure starts to drop. Other than that the only threat to the fish is trying to achieve the absolute maximum of CO2 in the water without affecting the fish - if you mess up doing that you can kill fish.


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## John N. (Dec 11, 2005)

You really don't hear much about end of tank dumps happening as much these days. I believe more people check their regulators every month or so, noting any drops in pressure and refilling it as promptly as possbile. 

There's really no need to double up on the solenoid. Just keep a monthly monitoring of the cylinder pressure, and for extra insurance you can purchase the Milwaukee pH controller to monitor a sudden decrease of pH as a result of excess CO2.

Truth be told, pressurized and DIY CO2 systems are pretty safe and will not harm a tank as long as regular monthly checkups are made, and in the tank is monitored for gasping fish as a result of too much CO2. Airstone on a timer that goes on at night will also help minimize pH swings if you're worried about that too.

-John N,


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## dodgefreak8 (Jul 26, 2006)

I have about 320 watts over my 220 which I hear is fairly high for a large tank. I don't dose co2 now though and I have no problems. I figure a smaller amount than normal can't be real bad.


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## hoppycalif (Apr 7, 2005)

In my opinion, based on what I have read on this and other forums, you can use lower CO2 levels without expecting serious problems from it. The secret is probably to keep a steady CO2 ppm in the water. The problem is knowing what ppm of CO2 you actually have. If it were my tank I think I would look at injecting enough CO2 to decrease the pH of a degassed tank sample by about .5 to .7. That should give you between 5 and 15 ppm or so. And, that isn't nearly enough to bother the fish, especially if you shut off the CO2 when the tank lights are off.


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## wiste (Feb 10, 2006)

The safest method would be to use a pH controller and run an airstone/airstones 24/7 with the CO2 turning off with the lights. Running the airstone 24/7 will consume more C02 but you could go to running the airstone only at night once you are comfortable that the system is under control.

When initially setting up a system, set it up on a day when you will be around to check the system frequently. Even better, be around the second day to check the system periodically.

If you are not familiar with the regulator sometimes it can be tricky to get a stable rate. 

A couple of times when first setting up a system, I left the room with a couple bubbles a second to come back in an hour later and find the rate had increased dramatically. This setup was not using a pH controller, which should be safer. 

If the tank is more about the fish than the plants I would go without CO2 injection. You do not need CO2 injection to grow plants.


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## TWood (Dec 9, 2004)

The end of tank dump hysteria was started by a supplier who did not originally include a needle valve in his CO2 delivery system. The needle valve acts as a 'gate' to prevent a large amount of gas from passing through, and also provides the needed back-pressure on the regulator so it doesn't get confused. 

If you connect a diffusor straight to the regulator without a needle valve in between, when the CO2 cylinder runs out of liquid and the pressure starts dropping, the regulator mechanism interprets that change in pressure on the high side as more demand on the low side, and increases flow. A diffusor can't provide enough back pressure to contain that and lets the gas flow, causing the regulator to open up some more to meet what it detects as more demand, and also to maintain pressure on the low side. Which causes a spiral into an uncontrolled dump. All resolved by a needle valve. I run my CO2 cylinders to completely empty every time and never had a dump - through a system that includes a needle valve.


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## dodgefreak8 (Jul 26, 2006)

thanks for all the input. I don't think I will need an airstone due to the fact that I run 2 xp3's with spray bars, one large sump filter and an emp 400. I think I will probably struggle to keep co2 in the tank. I'm just glad that these don't seem to be as dangerouse as some people make out.


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