As title really. I have started using it on my u3 but can't decide if its a good idea or not? Is there any benefit to it? It's bloody noisy I know that!!
There's no need, the bubbles that are drawn through are so large and are in contact for such a short amount of time that they have a minimal affect, so a waste of time really, there should always be sufficient oxygen in the tank, without any form of agitation/air stone etc, but rippling the surface of the water will increase the gaseous exchange.
The impact they have is negligible and they serve no real purpose other than to make a hideous noise, as long as you have some form of surface agitation you're fine.
I have a fluval u4 with the venturi on and you can't hear in when the lid is down. I dunno if it benefits them at all but it surely cant harm them. Some of the fish I had used to swim mostly at the surface, since I've had the venturi on they tend to sit lower down.
I don't run my venturi all the time. I just use it to agitate the surface for a bit then turn it back to the spray bar option. I wanted to use it as a protein skimmer but I'm not sure how that would work so just doing some research to make sure it is set up properly then use it for those purposes only. We are getting an air pump to go with a volcano I have bought to go in as in ornament. This has an airstone with it and will use this as more agitation for the tank surface as when I have the spray bar on my u2 surface agitation is not as strong. I plan to not have it too strong as my gourami didn't seem to like it too much earlier. I'm not sure if this is because it was the first time I used it or no.
I've got the U3, and if you fiddle with the rubber valve postion and position of the outlet to the water-line, you can drastically reduce the noise.
I only use mine in 'emergencies' now. I've been finding my 305 is starting to clog regularly (from bits of vallis) and one of my neons is a good indicator of oxygen levels, when the 305 reduces flow he can be seen gasping, so I quickly put the U3 back in with the venturi to oxygenate the water until the 305 is unblocked. Does a good job of it to.