Hi, I have a small outdoor pond- approximately 100 gallons- with a simple pump and waterfall but no filter. I've had goldfish in it for decades. I only "clean" it about every year or so, even tho I know I should do it more frequently. The water is rarely clear due to sludge, but when I do clean it up (remove about 1/2 the water and as much sludge as possible) it makes it even worse from stirring up the sludge. I also use microbe-lift pretty regularly. Long intro to short question: can I put in a algea/pond scum- eating fish like people have in tropical fish tanks? Will it help or should I just get more diligent about cleaning the pond and water.