In natural garden ponds most of the time there are fishes, which are sensitive to dangerous chemicals. So the pests control should be done using types of oil-free, biological insecticide. Detergent-based pesticides can damage plants like lotus and Lilly. It will be wise to void these products. Bt (Bacillus thuringiensis) is one of the best biological insecticides which is effective in controlling and eliminating pests, including spider mites, mosquitoes, and caterpillars. It can be directly sprinkled on to plants and into the water.