Two spring equinoxes ago we had a green algae profusion multiplying across the pond, which had taken on a fluorescent neon glow all over. The algae was thick at the bottom and had made its way to the top, where it was spreading.
We think it had this growth burst for a few reasons, one being that we had siphoned water to our garden the previous summer and that had lowered the water level considerably. This made the shallows shallower and being in full sun perhaps warmed to optimal algae temperatures. Being shallower the aquatic creatures moved away to where conditions were more to their liking, which would have made the shallows stagnant . .. good breeding grounds for the algae to take over. The resident ducks had been dinner for a wandering fox that winter, which had been a particularly long one where the pond had remained covered in a thick layer of ice from December till early April . … trapping all the goo, poo, gases, etcetera beneath the ice in 55 degree water.
Whatever the reasons, the pond ecology was obviously out of whack, disturbed, uncalibrated, etcetera, so after some learning we chose to add koi and catfish to the pond as a re-equilbriating, clean up team, the reasons being these:
the catfish would muck up the bottom of the pond, disturbing the algae points of origin
the koi would eat the overabundant algae as a food source . . . . this was guesswork based on the koi being carp family, and carp are supposedly algae eaters but being unavailable in Virginia we substituted with koi
We introduced 6 koi about 6″ long and a dozen catfish into the pond and the algae has vanished to the visible eye!! The catfish we haven’t seen since we put them in, but the koi have bred and there are dozens and dozens of them. They like to gather under the branches of an enormous autumn olive bush by the banks, out of sight of the blue herons that fly around looking for a meal. The wood ducks that liked that spot have moved under the bush further down. And the branches of the bush all around the koi gathering are covered with clusters of eggs . . . . are they koi eggs or frog eggs? We’ll have to wait and see, though every now and then we spot a newt feeding on them!