Is this enough sump?

[Toby_H]

The green intake is exactly what I described...

If all 3 overflows were built like the green one... and if your pump was strong enough... the water in the tank would slightly surpass the height of the 45* which would create water movement at the top... although not skimming the surface.

Personally, I would rather have the extra waste removal at the bottom than the skimmer feature at the top... but functionally speaking there is nothing wrong with having the standard overflow [as a "surface skimmer"

In my experience, any overflow that sucks air, is loud... also any overflow that sucks air allows significantly less water flow down it... so you will most likely want to set it up in a way that doesn't allow it to suck air. Generally this requires some sort of a "cap" and a pump strong enough to keep up with the flow the overflows take down...

I think you will find the pipes at the bottom take in quite a bit of water and the current from an airstone is not enough to add any noticable benefit... but there is no harm in doing it... if you like it keep it, if not take it out... no harm done...

If you start getting freaky with backgrounds and air pumps... spend a few minutes reading about "underwater waterfalls in aquariums". They use air to lift sand and water then let the sand fall out through an opening making a "sandfall" that looks like a "waterfall" underwater... they're pretty neat...

 

[Redoog]

oh you just have to keep throwing more diy ideas at me huh.

The third overflow, should only move a trickle of water. Chompers uses a setup like this and claims it is silent. Having the one higher at the surface, allowes the water level to be higher then the other 2. Since they are moving all the water, keeping them below the surface is the key to them being silent. All the valves I plan on using should allow me to calibrate the system.

 

[Toby_H]

The third overflow, should only move a trickle of water. Chompers uses a setup like this and claims it is silent. Having the one higher at the surface, allowes the water level to be higher then the other 2. Since they are moving all the water, keeping them below the surface is the key to them being silent. All the valves I plan on using should allow me to calibrate the system.

In my experience... having an intake slightly below the surface allows the intake to create a whirlpool down into the water eventually sucking air... which results in a very annoying slurping sound...

You can lower them enough to remove this possibility, but keep in mind when you turn the pump off the tank will drain down to the "overflow" point at the first T on your riser, or the highest point of your lowest intake point (whichever is lower). If your sump has the volume to accomodate this excess water then you're all set... But this would require running the sump fairly low...

Having the 45* intakes only slightly below the surface would mean you have less"extra" water taking up room in the sump when you turn the pump off.

I've yet to "perfect" this approach, but what I'm toying with is... placing a "cap" over the intake (in your case the 45* fitting) that is considerably larger in diameter than the opening in the pipe... In experiments I've cut the bottom off of a disposable cup and used it... as well as a plastic bowl (cereal bowl sized). The larger the "cap" the more effective but once you reach silent larer holds no benefit. This increases the "surface area" of the intake and also redirects the current... which discourages/prevents the whirlpool affect...

As I mentioned before, It's usually around the 17th attempt that you finally get it the way you want it. Sumps/Overflows can be custom modified to/for just about anything... it just takes time and creativity to get them just the way you want them...

As long as you enjoy the tinkering, you should be fine...