Is that the plan?
Yes
If so I would not plumb them at all, a sponge filter after met is all you are gonna need for up to 60 days. Leave them independent so you can easily remove each one for cleaning before the next hatch goes in.
Awesome tip, Makes all the sense in the world. Thanks, consider it done...Or not done
Since you don't need all four 20's for a while yet I'd get two more pairs as "back-ups" and place them in the last 2 twenty gallon tanks. By the time you need those tanks for growout they could already be spawning!
Another great tip, I was actually considering keeping most of the original 14 from batch 4. Thought of trying to pair them up and split my rbta to sell off as paired set with hosting rtba, thought that would be cool to watch them full grow and your extra 20 tip will give me that room. Sound like a good Plan?
Then you can quit your day job and be a rich clownfish mogul like Kathy
Ya, it's nice to dream, but I'd rather set my goals to an achievable goal!!

Although, the accountant would like zero taxable income.
Is the sponge filter for the tens with a stand pipe, or is that a hang on type?
How would you recommend piping the 4-20's? with stand pipes centered and top side loop inlets?
Tanks for the great info...Carl