As for the sizes, 400-500 on the barrel and 200-300 in an active res.
But forget flooming my dude. Build Venturi valves for them, with reeeeeeally long intake tubes so you can get them down center or bottom of the barrel. They bring in SO MUCH oxygen bubbles without an air pump its ridiculous.
Here's how you make em bruh:
Youll need,
-A few(4) 3-6" lengths of 1/2" black vinyl hydro tubing. EBay sold by foot $3ship
-2 3-6" lengths of 5/16" black vinyl tubing.
Also on eBay same seller.
-4-8Feet of 1/4" irrigation line. Home Depot
-2 poke through connector couplings for the irrigation line.
-the specific tool for poking holes in tubing for a tight seal with the couplings.
-roll of Teflon plumbers thread tape
-one set of MARINE HEATSHRINK TUBING from Harbor Freight.
-A sharp sharp blade and that's it!!
Then you just build this:
View attachment 4320197 View attachment 4320198 View attachment 4320199 View attachment 4320200 View attachment 4320202
You should be able to get the jist of it with those pix I'd have to think. But then when it's built, you can cut the lengths of 1/2" to whatever size you want for a short one or a bit longer. The smaller tubing is really only 2-3" long, but start with bigger pieces and cut down. Just make sure it slides into the 1/2" tubing about an inch or so. Be sure to use the Teflon tape here like in the pics to get a VERY snug fit.
The most important aspect you CANT FORGET is shown in one of the pics on the poke in coupling. You'll notice it has a 45* angle on it. You'll need to cut that. Buy a bag of 10 of these (minimum anyways) and try different angles to see what you like but that is the whole concept of this design. The water is compressed from 1/2" down to 5/16" and the coupling draws in air to compensate for the reduction in pressure. So when you stick this on the end of your 1/2" fitting on the pumps, which should both have that size at those gphs, it shoots out oxygen rich aerated water. Make sure that length of irrigation tube is long and above the water level maybe hanging off the edge of the barrel and taped half way down the side or whatever. Just needs to be able to pull in air. You'll also notice when you turn that coupling 180*, it will instead squirt water FROM the tube instead of pulling air in, so that's kinda cool. Just make sure it's the right way and feel free to epoxy or some kind of waterproof seal it in place and get a good seal on the connection too. You'll be able to tell as you turn it when it's at the best spot and delivers the most bubbling.
That took effort to reply. Hope you go this route. you'll be happy you did.
Take a few pics if Ya do and let us know how well it worked for you. It's literally a 5 minute build. No tools. Lighter works fine to shrink the tubing but a Heat Gun is obviously ideal and better for sure.
You MUST use marine grade heatshrink though because it has glue on the inside wall that melts as well as shrinks to form a water tight seal. So make sure you get it fairly warm to melt that glue good and evenly.
