I have never seen anything growing in the trash can. I keep it tightly covered, and is in an unheated part of the basement. So it gets no light, low temp, and no nutrients in the water for anything to grow.
I go through it quite fast. There is probably only 20-25 gallons in the can as I did not fill it all the way up. I use 7 a week for the SW
, and I use another 7 for my 50:50 mix in my FW
Tank...and a friend comes and gets 7 gallons every other week. So I think the water turn over is quite good.
I think a powerhead will help...and I may find I need one in the summer when things are a little warmer. So far...every time I have tested the water...it was always read 0ppm. There is no smell at all to it.
So...so far...I had no trouble keeping that much water around. I use a JBJ Powerhead with a 1/2 clear plastic tubing to pump the water out of the trash can into my carrying jugs.
Hope this helps
90 Gallon Fresh Water Planted w/ CO2
7 Brilliant Rasbora, 6 Harlequin Rasboras, 3 Dwarf Neon Rainbows, 1 Red Tailed Shark, 2 American Flag Fish, 4 Skunk Botia Loaches
40 Gallon Breeder Salt Water: 4 inch DSB
(2/3 Agaramax & 1/3 Sea Flor), Bak Pak 2R Skimmer w/ BBX, 2 x JBJ PHs, Coralife Lunar Aqualight (2x96w), 30lb Base Rock and 40lbs of Live Rock.
Inhabitants: Purple Firefish, Pygmy Angel, Lawmower Blenny, 2 Cleaner Shrimp, 1 Peppermint Shrimp, Pistol Shrimp(HH), 1 Emerald Crabs, 3 Porcelin Crabs(HH), varying amounts and varieties of hermit and snails.
3 Gallon Eclipse:
1 Goldfish (won free at a fair...cost $50 in equipment)