about 3,000 gallons.? i've had it near 30 years. it has never been real clear [ i have No filter system, cant afford one] this year it has a green "algae" growning in the water..i can only see the fish when they come to the serface to eat.. they seam otherwise healthy.. but i qwould like to clear the water.. i have "dosed it 4 -5 times with an algae killer and once with a treatment that is suposed to eat up dead algea..nothing has worked even a little.. how can i clear my water [it has been relatively clear for near 30 years] without the use of a filter which i cant afford..?