Help with system design - 25g

[syncro]

Any suggestions/criticisms/tips/feedback on this new tank and sump design?

25g display tank (glass, low iron, polished edges)

17g sump (glass)

Tank with cabinet and sump


Overflow
The overflow is a bulkhead with overflow box around it to set water level. Here is an example. Similar to gl*******s kits but the overflow is not sealed to the bulkhead. When the return pump fails water will eventually drain down to the level of the bulkhead. The sump can accommodate this drainage. Overflow is removable, adjustable and cleanable. The choice for this overflow is mostly asthetic - small footprint inside and outside the tank and easy to clean. Target flow through sump is around 90gph. Gl*******s claims 300 gph with similar design. Additional flow in display tank with powerhead.

Sump
3 chambers plus ATO reservoir. Bubble trap.

Stand
Existing IKEA stand pictured here.

Questions

• Is the skimmer chamber the right size? Water level will be 9" high. No idea what skimmer I will run. Pictured in the diagram is a Bubble Magus NAC3+ (25g - 80g). Can you design a general skimmer chamber or do you really need to choose a specific model and design around it?
• Is 2g ATO enough? Would like enough water to last 1 week. On my 5g I use 0.25g per week.
• mike31154 suggested a gravity ATO. Make a smaller glass tank that sits on top of the sump? Enough room for plumbing and general room to work?
• Any other suggestions, especially on the sump.

Thanks!

[beefORchicken]

i have a 25g and my ato is doing something very close to 2g each week. you might be ok, or if you want to be really safe you could make it 2.5g

[FishyFishy!]

If you're going to have external plumbing anways, why not do a herbie system with and external overflow box? Simple box on the outside with two drain holes - one for main drain and another for emergency. Then keep the drilled hole on the right side for a return. It would also clear out some space inside the tank.

I would personally go way bigger with the ATO. 2g is not enough. You would most likely be filling that every second day.

I've done a couple gravity fed ATO's, and I can say by the time you're done with the headache, you might as well find a used Tunze ATO for cheap.

[syncro]

An external herbie would support higher flow rate and be quieter at those rates. Asthetically, it is very clean inside the tank but I don't find it as appealing when looking at the tank as a whole. I really like the glassbox look and even considered lily pipes. Will the overflow above cause any problems at low flow rates?

I'll increase the size of the ATO to 4 or 5g. What headdaches are there with gravity fed ATOs?

Thanks beefOrchicken and FishyFishy.