Targetted, fish-safe bacteria is held within dunks and released into water when added. To treat fungus gnats, crumble 1/8th of a dunk into a litre of water and leave to brew for 30 minutes. Afterwards pour your mix through a sieve, or skim off any bits and use the water to treat plants.
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This contains BTI (Bacillus Thuringiensis Israelensis) solids, spores and insecticidal toxins. Usage: 1g will cover 1 square m of soil surface, so this must be used sparingly 1 thousandth of a gram can kill thousands of pests, so no need to overdose.
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