Curiosity and help

[NashobaTek]

Instead of sucking water into a regular undergravel filter, the flow is the opposite direction blowing water out of the sand. Not widely used anymore but something i would consider in a smaller tank. Problems with it are you need a coarser sand, idk if wrasses like undergravel flow, and some corals placed on sand may or may not like it depending on flow strength, but it keeps sand free of debris and increases flow below high flow corals you may want to place lower in the dt.
I think those are the pros/cons lmk if i got anything wrong nashoba

You're pretty accurate. It helps keep the sand clean and detris in the water column for the hob filters to pick up. It doesn't require a sump.
It's definitely a old school method but it's what I started with in the 80's.

 

[ying yang]

Just go to google and type anything you want to know.
On a couple my tanks i had stickers on bottom glass saying was tempered do not drill but cant guarantee all say this.
Lots youtube videos on drilling tanks also.
Just remember to keep glass wet to cool it down while drilling.use play dooh or plastercine or anything to make a dang to keep water in but if google " how to drill glass tanks " will explain and show step by step guide how to do it