Questions - Need some input

Hello everyone I am working on a new sump for my 75 gallon tank. Here is what I have come up with. My question is this do I have a the baffles the correct? I have reef octopus skimmer 6 rated for a 150 gallons and should sit in 6-8 inches of water. The two baffles in question are labeled
(red arrows in the picture) do they both need to be 8 inches high or are they good the way there are? let me know if anyone spots any other issues with this set up as I don't what to have the glass shop cut ...

Do you guys discard a DI cartridge at a reading of 1 or just keep it till it goes higher?
I remember reading about DI releasing ammonia (something about binding power) first when exhausted, Any truth to that?
If that's true then one shouldn't even have two inline as after the first is exhausted it'll just saturate the following one with ammonia?
Thanks for your help.

I'm getting ready to upgrade my tank from a 75 gallon to a 140 with a 40 gallon sump. I need to upgrade my skimmer and had considered building the CS1 from Avast. It's rated for up to 200 gallons and comes with a sicce PSK 2500 pump with avast modded volute. My intention for the tank is to concentrate on SPS and LPS corals. Any input would be helpful.

Well i got my skimmer in and I will octopus skimmer seems well built, it is a hurricone cat2e. The paper work that comes with the skimmer is extremely poor doesnt give you common application for install, gph feed rates. Well anyhow my question is about the output at 10in doesnt give much leeway for install and at 27in high i cant really put it on a stand. Can this output be raised with out messing up the operation of the skimmer. I havent build my sump or the plumbing done so i can make thing however ...

Good Morning Reef Addicts,

I'm trying to figure out what size return pump is needed for my 120 gallon tank. I have a 5 foot delivery head on a 120 gallon tank with 2 mega overflows (Oceanic Ultimate Series), which are rated at 600gph each. I found a blurb on Marc's site that I should have a return gph pump of 3x to 5x the display tank. The Eheim 1260 has a 635 gph rating but at 5 feet of delivery head it brings it down to about 400gph. This makes it about 3.33x the display tank. But ...