santa-monica filtration

I have a Surf4+ that I just took offline from my 300 gallon system. Worked good, but I've moved onto a Pax Bellum reactor. $550 new. https://www.santa-monica.cc/SURF4x-floating-algae-scrubber-and-seaweed-cultivator--4-cubes-feeding-per-day--Xtra-light-for-higher-nutrient-water_p_73.html

So I'm going to give this build thread a shot. I'll start from the very beginning. I teach a kindergarten through 5th grade science block. Several of my students have been asking for the last couple of years why I don't have a Nemo fish. I continuously have to explain that a Clownfish requires...