Who Gives A Fish Forums

hey its been ages since i last posted but i need a hand, i made a simple diy setup with 2 litre coke bottles but i'm stuck on how to stop the gas at night when the lights are off. i had a system going but it stopped working due to a bad algae buildup, my tank is a jewel vision 450. does anyone know of a system i can make to switch off the gas at night? i'm pretty new to all this plant stuff so if you could give me some detailed advice that'd be great, thanks.

I also run a DIY CO2 setup and I've found it's better to just leave it on 24/7, especially since I've got a lot of plants. The fluctuations in CO2 levels can be pretty bad if you turn it on and off, and to be honest, there's not really a way to shut it off at night without removing the bottle from the tank - otherwise, it'd just get stuck in there.

If you've got fish in the aquarium, you shouldn't be running CO2 when the lights are off. I mean, when the tank lighting isn't on full, that's what I'm talking about. You risk poisoning your fish, it's a pretty straightforward thing to avoid. I've learned to recognize the natural buildup of CO2 in the dark, it's flux, and that's why surface disturbance at night is crucial.

I think it's worth noting CO2 doesn't displace oxygen, so as long as there's decent surface agitation, running it at night shouldn't be an issue.

_SlowDoom wrote: ↑Tue Apr 19, 2022 7:13 pm I also run a DIY CO2 setup and I've found it's better to just leave it on 24/7, especially since I've got a lot of plants. The fluctuations in CO2 levels can be pretty bad if you turn it on and off, and to be honest, there's not really a way to shut it off at night without removing the bottle from the tank - otherwise, it'd just get stuck in there.

"CO2 does not displace oxygen" - that's simply not true. In the dark, fish and plants keep on respiring, using up oxygen and producing CO2. This reduces oxygen levels and increases CO2. Now, the dissolved CO2 binds with minerals like calcium, creating bicarbonates that raise hardness and alkalinity. It also binds with organics, forming carbonic acid that lowers pH. This daily fluctuation raises oxygen, hardness, and pH during the day, and lowers them at night.

In natural waters, this happens, but in an aquarium, it's amplified. You'd need a lot of surface disturbance to get rid of that CO2. There's no logical reason to run CO2 in the dark, since plants can't use it and it can easily saturate the water. We've all heard the horror stories of massive fish deaths overnight due to CO2 poisoning - it's a risk I'm not willing to take.

And then there's the pH drop at night, caused by all that CO2. A small fluctuation might be okay, but the increase in CO2 from artificial addition can cause a bigger drop, more than 1 degree, and that's bad news for the fish.

I don't use artificial CO2, but in the morning, I can see the increase in respiration from my fish, including more frequent breaching of the surface by my Corydoras, all due to the increased CO2 from the plants overnight. It takes a lot of surface disturbance to dissipate this, and it's even less likely to happen when you're adding artificial CO2 to the system at night.

I was mistaken when I said CO2 doesn't displace oxygen, it actually does. When fish breathe, they take in oxygen and release CO2, which in turn makes CO2 more abundant. However, in the absence of fish, oxygen can indeed get replaced by CO2, as has been proven in various studies.

You don't need extra CO2, trust me, there's plenty in your tank.

The air pump's already pumping it in, fish are breathing it out, and decaying plant matter's releasing it too. Do you really need more?

As a fish keeper, my tanks are all about the fish. If a plant's struggling, it's gone. I'll get a new one that's easy to care for.

If your fish need a low-light, low-current tank, that's what they should get. Choose plants that fit.

I'm with boomer on this one - the less you add to the water, the better.

Check out my tank - low light, barely any current, no CO2. Just 5 drops of Seachem Flourish every 2 weeks. My plants are thriving, 2 feet tall at the back.

I've come to realize that my DIY CO2 setup might be more trouble than it's worth. Looking at the potential risks and issues, I think it's best to take Nick and boomer's advice and ditch the DIY CO2. The fluctuations can indeed lead to black algae, and I'd rather avoid that hassle.