Well I have gas!
I was running Co2 on my old tank, but as it is a 450 liter tank I had a relatively small bottle. If I was to simply try and use that system on this tank the gas would be gone in a flash. So I needed a bigger bottle, and also to work out a way of delivering enough Co2 into the water with out too much loss of gas.
I did a trade in on my old bottle for a much larger one, so that solved that problem. All fittings, and regulator I took from my old unit.
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Next task was to sort out a way of getting the best possible dissolve rate in the water. I didn't think that the usual ceramic diffuser would cut it. I am also keen not to have any pipes, tubes, wires, etc. in the tank. I want to keep everything contained in the sump out of site. I looked at some inline Co2 reactors on the internet, and decided to go down that route. However it would be easier and cheaper to build my own.
So I knocked up a reactor using a wide section of pipe, with 2 step downs on each end, so that I could plumb it in to the return pipe, just above the pump. Inside the pipe would go some bio balls, and a small feed valve connector to connect the Co2 hose on to. The way it works is the Co2 enters the bottom of the pipe where the water flow then pushes it through the bio balls, and the bio balls in turn break up the bubbles and swirl them around. This I hoped would give a good dissolve rate. After the reactor the water then has to travel along something like 4 meters of pipe until it gets to the tank, so has even more time to absorb the Co2.
Just a couple of quids worth of bits:
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Assembled:
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Plumbed in just above the water pump from the sump:
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I tested the system and there is only the slightest mist of bubbles exiting the pipe outlet in the tank, so I am fairly confident that I am getting as good a dissolve as I can, and not wasting gas. Time will tell once I have had a chance to run it for a few days. The regulator is controlled by the pH controller, and the sensor for that is positioned in the final part of the sump. So it is measuring the pH at the very end of the chain at the point where the maximum amount of gas loss will have already happened. I am sure it will need some tuning, but I will do that once everything is completed.