Question
I have inherited a pond, that is about 20ftx20ftx1-4ft.  Lined with pond liner.  Has pump, waterfall, biofilter, lilies, lettuce, other vegetation, and about 20 (they keep procreating) goldfish.  I have a big problem with suspended algae, in spite of MUCH and repeated enzyme treatments of several sorts.  Any ideas?

Answer
Hello Anne. As a person with ponds, I feel your pain! There are several things you can try. Enzymes and beneficial bacterias are usually your best bet for suspended algae. I can give you a few instances where they would not be very effective: 1) if the pH of the pond water is above 8.0; 2) if less than one-half the pond surface is not covered with aquatic plants; 3) Inadequate filtration system; 4)Heavy fish load.

Here are a few things you can look at:
1) What are your aquatic plants potted in? Top soils/potting soils do nothing but feed algae. Make sure your using an aquatic mix that forces the aquatic plants to get their nutrients from the water versus the soil.

2) What type of fish food are you using? "Bulk Foods", catfish foods, or any other fish foods (especially flake foods) usually have high amounts of filler and the fish pass more of the food through instead of digesting it.

3) I mentioned pH already. This is probably one of the most important and neglected measurements with regards to algae.

4) Check your nitrite and ammonia levels. If your levels are high enough to show up on a test kit but too low to affect the fish algae can run rampid.

5) Sometimes all your water quality factors can check out good, the plant coverage can be adequate or even text book, filter systems in place, and suspended algae is STILL a problem. The only thing to do in this case is change something that effects the load on the pond. Add a component to your filter system, maybe a skimmer, or add more plants, take out some fish. Sometimes changing the frequency of use with regards to the enzymes/bacteria used helps. Remember this: application rates for beneficial bacterias and enzymes are usually "suggested". They are natural products and therefore using them more frequently than the standard biweekly or monthly application may help if the load on the pond is heavy.

Anne, this turned into a short novel! Hope this helps!