also is co2 poisonous

[LMOUTHBASS]

to fish if you dont know what your doing with it

[anonapersona]

Co2 will add acids to the tank, this can use up the buffer (KH) and lead to a pH crash.

It is also possible to overdose the CO2, find a CO2 chart and locate your pH and KH, when you add CO2 you will move along the KH line to a new pH and a new CO2 level. If you add too much Co2, going too far along this line, you enter dangerous territory where fish can die.

DIY CO2 is harder to turn down than pressurized CO2, so you have to start small and increase if needed. The Hagen system is OK for 20 gallon tanks, I have that on my 20 and my 10. It can be turned down, sort of.

DIY CO2 is harder, you have to change out the mix to reduce the rate, or change the surface agitation or filteration to allow more CO2 to gas out. If you have a HOB filter, you probably can't OD the CO2 unless you really tried, but a cannister filter has less agitation at the surface, more CO2 stays in. It is all about balance, that is why each tank is unique.

[djlen]

There are a number of ways to decrease the CO2ppm in the water table. Two of the most effective revolve around gassing off the excess. If you have a HOB, increase the flow rate to the max. Also you can lower your water level so the water will splash into the tank. This will increase the surface agitation and assist in the gas off. If you don't have a HOB, add an air-stone and the bubbles rising to the surface will serve the same purpose as above.
As anonapersona says it is very difficult to control the feed of CO2 when using a DIY system.
Len

[superjohnny]

I think the general rule of thumb is if your tank is bubbling like a hot-tub there is too much CO2. :D

I wouldn't even bother trying to control the flow rate on DIY... there's never going to be enough CO2 to kill fish. One thing I like to do is use two bottles and stagger when I refresh them. I have 2 bottles and a T connector. Every week I change one of the bottles. It gives me a more steady flow of CO2 compared to one bottle. I would think more than two bottles would be more trouble than it's worth.

[anonapersona]

Originally posted by superjohnny
I think the general rule of thumb is if your tank is bubbling like a hot-tub there is too much CO2. :D

I wouldn't even bother trying to control the flow rate on DIY... there's never going to be enough CO2 to kill fish. One thing I like to do is use two bottles and stagger when I refresh them. I have 2 bottles and a T connector. Every week I change one of the bottles. It gives me a more steady flow of CO2 compared to one bottle. I would think more than two bottles would be more trouble than it's worth.

Unfortunately I've read some firsthand accounts from people who have killed fish with DIY, typically with softwater and large volume generators. Amazingly enough, one was a 50 gallon tank. The theory before that was that DIY was insufficient for tanks above 30 gallons!

While bubbles from plants do indicate excess O2 (or simply mechanical damage to leaves so that air escapes) it is not a reliable indicator of excess CO2. Unfortunately, the first reliable indicator, if you are not testing pH, would be fish belly up in the tank. Often this is first noticed in the morning, or after being out for the day. (So, do all changes to the CO2 system in the morning when you will be around to see that all is well.)

Sometimes people will notice fish distress after making changes to the input method (new reactor design or location) or eliminating surface agitation (switching from HOB to canister). I've even read of people having problems with fish distress after installing a well sealed glass top, so that air exchange was limited. I'll admit that some of these later examples might have been in tanks using pressurized CO2, I just don't recall for sure, but the cautions are real nonetheless.

I am very quick to point out that this stuff needs to be monitored, you need to know your water parameters. That said, foam-ups have probably killed more fish than pure OD's have.

[Starry]

Originally posted by superjohnny
I wouldn't even bother trying to control the flow rate on DIY... there's never going to be enough CO2 to kill fish.

You have to be careful with that. Even with a KH of around 5-6, a freshly made Jell-O mixture can get my 10-gal tank to pH 6 or so, from pH7.4+. That's a lot in just a few hours, and even worse if it happens overnight when the plants aren't using it.

Anonapersona had a very good point - change your CO2 in the morning, and monitor the tank and fish throughout the day. If anything seems off, disconnect right away, just to be safe. Another good thing to do is to increase surface agitation when you connect the new CO2, then gradually decrease it over a few days until you get the pH you want. That way you don't get a quick pH change. On a larger tank it's not as drastic.

Usually DIY CO2 won't be dangerous, but you should still take precautions. With pressurized, if something goes wrong, it's much worse.

Also, before you start up with CO2, make sure you understand it! Understand the chemistry and biology - the relationship between KH and pH, how CO2 affects it, the needs of plants vs fish.....

[anonapersona]

Originally posted by Starry

Also, before you start up with CO2, make sure you understand it! Understand the chemistry and biology - the relationship between KH and pH, how CO2 affects it, the needs of plants vs fish.....

I find it so ironic, I never liked biology, and I absolutely HATED chemistry, and yet that is what I must (volluntarily) understand in order to keep a planted aquarium.

There must be some Karmic Law at work here. (Be careful what you think you hate, for you will be required to master it. -- ?)

[Starry]

Originally posted by anonapersona


I find it so ironic, I never liked biology, and I absolutely HATED chemistry, and yet that is what I must (volluntarily) understand in order to keep a planted aquarium.

There must be some Karmic Law at work here. (Be careful what you think you hate, for you will be required to master it. -- ?)

Actually, understanding the biology and chemistry of my tank and plants/ fish is most of the enjoyment to me. I'm naturally a scientific person, and I can't imagine not understanding what's going on, just blindly buying cycle and ick medicine because that's what the fish store sells. It's awesome to be able to see so much of my study field in a hobby. Who even needs a lab? :)