In a simple pond ecosystem, the big fish eat the little fish and the little fish eat the algae, bugs or other small plants. However this all changes the moment a pond gets overgrown with weeds leaving the bigger fish at risk.
With overgrown plants, which turn into weeds when there are too many, the big fish are unable to find little fish that are hiding away in all the plants. Most of the big fish need those little fish to survive and without them stunts their growth, leaving pond owners wondering why the fish they catch are so small.
“The weeds are really important for the fish to be able to hide and ambush,” Kansas State fisheries extension specialist said. “If you have too many weeds, the little fish aren’t going to leave the home because they are going to be able to hide in all these little places.”
Plants in a pond aren’t an issue, until they reach 20-25 percent coverage of the water making those aquatic plants start to turn into aquatic weeds. Besides just places to hide for the fish, too many plants also can cause issues of oxygen levels that take out some of the air in the pond that the fish need.
“During the day they photosynthesize so they give off oxygen, but at night they transpire and when they do that they use up oxygen so they can make that oxygen cycle a lot steeper which can cause problems with your fish as well,” Gerken said.
Luckily there is a way to solve the issue by either raking out all the plants in the pond, which can be a lot of work, or by using a pond and fish safe herbicide to kill off the plants that aren’t reachable any other way.
“It is a lot of work, but it gets those nutrients out of the pond itself and so removing them from the water shed where they can decay and then turn into really good compost,” Gerken said.
While it may seem odd, getting the weeds out of the water isn’t something that can be done at any time because of how it can affect oxygen levels. Making sure that there is a proper management plan in place to safely remove the weeds is important and will help to keep your pond safe and the fish happy and healthy.
