is Reverse Osmosis. DI
is De-Ionized water. RO
is when you have both together in the same system.
It's a filter for your tap water. There is TONS you can read about it here and other places online.
My tap water has a Total Disolved Solids (TDS
) reading of 219. For lack of a better word, TDS
tells us how pure the water is where a zero reading is perfect.
The water that exits my RO
filter is currently ready about 6, but I expect it to drop to 1 after another day or so.
I would recommend trying to use something other than straight tap water for your salt-water tank.
I got my RO
filter on eBay for about $100.