- It was initially an experiment to make a plankton-friendly system. The Artemia were my (poor, on reflection) model.
- It was the whole 55g tank, plus a 10g sump in Phase II.
- The trick to artemia is not so much water quality, nor oxygen (they can surface-aspirate). The trick is to make sure they get enough food. And they only eat algea and bacteria.
Most airline bubblers actually make bubbles so small they can clog the feeding filters of the Artemia. You want relatively large bubbles, slow water movement - and plenty of light to fuel the growth of phytoplankton.
NO POWERHEADS! They will just blend the poor critters. A Hagen Aquaclear 802 will kill Artemia greater than 1mm, and even solids-passing sump pumps will kill Artemia greater than 3mm in size.
If you have no plankton, go to any LFS, and buy some cheap critter (ie a blue-legged hermit crab) from their scuzziest tank. It'll have plenty of plankton, and the hermit crab will eat the cyanobacteria film in your tank.
Anyway, 'charge' your tank with phytoplankton from the hermit crab's water for a week with good lighting, and then add your artemia. A very *tiny* amount. Like the tinyest pinch for 55 gallons. Overpopulation is a sure way to kill them all - they will out-consume their food source!
For more info (mostly commercial), see the Artemia section of this site.