Are dual stage regulators absolutely necessary?
Is an end of tank dump a real issue on the smaller 600g canisters? Why would CO2art sell single stage if there was a risk to fish?
Its a JEWEL 125 with the LED strips rather than the T5, adding liquid CO2 seems to have helped the plants a little, there is new growth and less algae.
CO2Art only sell dual stage regulators, that’s where mine came from.
I don’t know if end of tank dump is a problem on smaller containers, I don’t see why it wouldn’t be. Given they are more expensive I’m not sure why you would want to go down that route. A 600g tank will not last long on a 125L.
Are they the Jewel LEDs or have you retrofit something else? How much wattage do they have?
Also what’s your photo period and what plants are you trying to grow? Does your tank get a lot of natural light?
Sorry for the 20 questions but it helps when trying to see what your set up is and what you are trying to do. A lack of CO2 may not be the source of your algae problems/lack of growth.