So I never thought it would happen to me! I set up the tank and had the nasty air sucking noise even with the low flow in the paludarium. I have my return line plumbed with a tee where one line goes up into the main tank and one line goes back into the sump, the line that goes into the sump has a valve so I could adjust the flow to the main tank. The problem is that that valve is opened all the way up and I still have more flow than I had originally planned for.
If anyone wants to look at the build to get a better idea of the tank/sump here is a link:
I don't think I can live with the noise so I am thinking I have a few options.
1. I could get a smaller pump I have a Danner mag 350 and think I could downgrade. I was worried that if I went smaller I might not have the power to overcome the head pressure. The only problem with this is I bought the pump over a year ago so not sure If I can return it. The pump failed so I am currently waiting for a new one under warranty. The only problem with this route is I am not sure this will solve the problem. I don't need a lot of flow and am thinking the less flow the less air getting sucked down the pipe = less noise.
2. The line that goes into the sump is currently plumbed into a tee that is embedded into the hamberg matten filter in the sump. My thought with this was that this would act as a little trickle filter and provide a little extra filtration. This is definitely not necessary so I thought maybe taking it off would lessen the flow slightly since the water could travel more freely out of the return. Not sure how much of an effect this would cause.
3. I could make a modified durso by plumbing a tee into the bulkhead. From what I could find with a quick search it looks like It would have to be a MPT and 2 slips. The MPT would go into the bulkhead and one slip would be the return to the sump the other slip would be where air would enter. If I tried this could I just leave the second slip completely open or would I need to cap it and use an airline regulator to control the flow of air into the system.
Sorry for the book and hopefully this make sense to someone, any help would be greatly appreciated.