CO₂ injection for Dutch style aquarium

Question

My local fish store is having their every other month sale of $1 per gallon regardless of shape, and I am considering picking up a 40 gallon (around 151 liters) breeder tank in order to set up a Dutch style aquarium, which is a style I've always wanted to try. (Note: No affiliation with the link, just a decent article on the style.)

I will either get a 20 liters (around 5.3 gallons) tank as well and build a trickle filter into it, or get a used one from another LFS that sells used marine tank equipment.

With that style of aquarium, CO₂ injection is almost mandatory, but what I would like to know is if the CO₂ injection has to be into the tank, or can it be done in the sump? I would assume that it could be anywhere, but I don't know for sure. I'd prefer having as few tubes running into the actual tank as possible.

Answer 1

Yes.

Yes, you absolutely can inject the CO₂ into the sump and many people choose to do this by default because, as you point out, it means less equipment in the tank.

As long as the CO₂ is diffused into the water and pumped around so that it moves past the plants then you'll have just as good rate of diffusion as if you had the injection setup inside the tank.

You may find that you can actually get a better diffusion rate because the equipment in the sump can be less styled and more fit for purpose. Some of the development work for products like JBLs CO₂ ladders goes into making them look 'nice'. In the sump (unless it is on display) you don't really need to worry about that and can use whatever method works best.

Some products like inline CO₂ atomisers are designed to be fitted to your filter return hoses to cut down the amount of equipment in the tank. In my experience these work really well (I owned an Up-Aqua one not the JBL one linked though) but just make sure that it is fitted very carefully to avoid leaking.