Ornamental ponds with no fish or plants may use a commercial algae control product added to the water. Fish and plant ponds require a different approach.
Step 1
Give the algae competition. For plant-only ponds you will need to establish a plant ratio that covers 70% of the water surface to compete for the nutrients that algae feeds on. The addition of beneficial pond bacteria can also be sued to compete or nutrients against algae. Other nutrient control measures can be done manually such as raking the pond surface or vacuuming the pond walls and bottom to remove muck.
Step 2
Keep a low fish ratio and do not overfeed. Fish ponds with or without plants benefit from low fish ratios. One goldfish for 100 gallons of pond, and one Koi for 500 gallons of pond water.
Step 3
Shade a fish pond that has little plant coverage with a pergola, a sail shade, or even pieces of styrofoam during the sunny summer months. Pond colorants can also be used to shade the water. The are mostly available in black and blue options and are non staining and non toxic.
Step 4
Plan on 10% water changes weekly during spring, and summer, using a dechlorinator before adding fresh water.
Step 5
Get an ultraviolet sterilizer unit. This is available at most pond websites and will control free floating single-celled algae. Combine this with an external filter for the UV unit for best results.
Step 6
Create your own external filter (look up "skippy filter" on internet) or buy one to help convert the ammonia waste that fish produce to nitrites, and nitrate. Control the resulting nitrites and nitrates with water changes, and add floating plants such as water hyacinth, water lettuce, or others to help consume excess nitrates.
Step 7
Allow your pond to become established. The pond walls will over time host heterotrophic and chemotrophic (beneficial) bacteria. Heterotrophs consume organic, carbon based waste like fish food, fish waste and dead vegetation, while chemotrophs will help remove toxins like ammonia from the water.
Step 8
Let the filter become well-established & remove algae. String algae or blanket weed algae occurs when free floating algae is controlled, but there is an excessive amount of nutrients in the pond. Allow your filter to become established and remove this type of algae with a toilet brush. Twist the string algae around the brush like you would cotton candy and discard it. String algae is most prevalant in new ponds and will usually be controlled as the pond matures.
Step 9
Add aeration to your pond. Aeration stimulates microbial activity and adds essential oxygen and circulation to the pond which deters algae growth and reduces anaerobic digestion of waste.
Warnings
- Plants add oxygen to the water during the day but consume it at night. Make sure your fish pond is well oxygenated with a waterfall, or airstones so that the fish do not compete for oxygen with the plants at night.
