Whitebeam said:
Simple question, but conflicting indications of the correct answer: Into which hose of the filter should the inline diffuser be inserted? Input or output? I notice that the Boyu is designed to replace the inlet strainer, suggesting the answer is 'inlet', with the filter acting as a reactor; but most of the posts I read have it on the output, so I guess the answer should be 'output'.
Peter
Good question!
Most inline diffusers are designed to be place on the outlet, so the CO2 microbubbles or mist can be distributed effectively throughout the water column. CO2 like this, in its gas form, is more efficient at delivering CO2 to the plants. It also means that one can run a comparatively lower dissolved CO2 level in the aquarium, yet still obtain enough CO2 for the plants.
However, this method does require excellent water circulation in the aquarium to enable the CO2 mist to reach
all parts of the tank and plants. In poor circulated tanks some plants will be getting plenty of CO2, others will starve and algae will proliferate.
I have noticed that in tanks with lower levels of circulation it's better to have the CO2 100% dissolved. It seems that the CO2 is more easily distributed this way, and all the plants stand a better chance of getting their required CO2.
This assumption is based on experience with various set-ups and differing CO2 delivery methods, from ladder diffusers, to ceramic discs placed at the opposite end to the filter, to inline diffusers place on the inlet and outlet.
For me the hobby is more about aesthetics than pure plant growth and gardening. So I have an inline diffuser placed on the inlet. This means I don't get millions of white bubbles all over, spoiling the aquascape. The trade-off of this vs. risk of the filter leaking (I haven't had an issue in over 7 years of CO2 being pumped directly into filters in one way or another) and better plant growth is worth it, in my experience.
So, in summary; if you want the best possible plant growth and have excellent water circulation, and don't mind seeing lots of bubbles floating about, then positioning your inline diffuser on the outlet is the better option.
If you want 100% CO2 diffusion and no bubbles then the inlet is an option.