Dunks for big, persistent water (barrels, fountains, drains (~100 sq ft, ~30 days). Bits for small, shallow, or already-infested water (bromeliads, saucers, gutters) fast release, 1–2 weeks). In South Florida you want both under the sink: Bits kill this generation, Dunks deny the next one.
The Matchup Table
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Both formats plus an ovitrap covers the full container-breeding cycle: kill the larvae you can find, trap the egg-layers hunting for water you can't.
Why Bti Is the One "Natural" Product We Recommend Without Hedging
Most products marketed as natural mosquito control earn a shrug from anyone licensed (we wrote up the gap in our natural mosquito control guide. Bti is the exception because its selectivity is biochemical, not marketing. The bacterial crystals activate only in the alkaline gut of certain fly larvae) mosquitoes, black flies, fungus gnats. A koi, a honeybee, or a golden retriever that encounters Bti simply digests some protein. That's why it's cleared for fish habitats and organic gardens, and it's the same larviciding logic our own crews apply to koi ponds and water features where spray is off the table.
The honest limitation: Bti kills larvae only. Adults are unaffected, and pupae, which don't feed, sail through untouched. Treat water that's already wiggling and you'll still see a hatch from the pupae that beat your timing. That's why the drop in biting lags treatment by a few weeks, and why finding every water source matters more than any product choice.
Still getting bitten after treating every drop of water you can find? That's adult pressure, our department.
Frequently Asked Questions
What's the actual difference between Mosquito Dunks and Mosquito Bits?
Same active ingredient, different delivery. Both use Bti (Bacillus thuringiensis israelensis), a naturally occurring soil bacterium whose toxin is lethal to mosquito larvae but essentially harmless to fish, birds, pets, bees, and people. A Dunk is a slow-release floating ring: it treats up to about 100 square feet of water surface and keeps releasing for around 30 days. Bits are corn-cob granules coated with Bti: they release fast, knock down larvae within days, but exhaust in one to two weeks. Dunks are the long-term garrison; Bits are the strike team.
When should I use Bits instead of Dunks?
Use Bits when the water is small, shallow, irregular, or already wiggling with larvae. Bromeliad axils, plant saucers, tray tables, gutters you can't clear this week, potted-plant reservoirs (sprinkle Bits and they work where a floating ring physically can't sit or would be comically oversized. Bits are also the right first move on water that's already infested, because their fast release kills the current generation before it pupates. Pupae don't eat, so Bti can't kill them) speed matters when you can already see larvae.
When are Dunks the right choice?
Standing water that persists for weeks and has real surface area: rain barrels, unused fountains, French drain basins, pond edges, pool cover puddles, boat bilges, the swale that never quite dries. One dunk covers up to ~100 sq ft for about a month regardless of depth. For Florida rainy season, dropping a dunk in each persistent water feature at the start of the month is about the cheapest per-day mosquito control that exists.
Are Dunks and Bits safe for fish ponds, pets, and bees?
Bti is one of the most selectively targeted pesticides available: its crystals must be eaten by a larva with the right gut chemistry (mosquitoes, black flies, fungus gnats) to activate. Koi, birds, dogs, cats, bees, butterflies, and humans don't have that gut chemistry. It's approved for use in fish habitats and organic gardens. As always, the label is the law: follow it, and don't dose drinking water.
Why didn't Bti stop me from getting bitten?
Three usual reasons. One: Bti only kills larvae: the adults biting you tonight are already airborne and unaffected, so expect the biting to fall over 2–4 weeks as the pipeline drains, not overnight. Two: you treated your water but not the breeding sites you didn't find: a bottle cap holds enough water for Aedes aegypti, and your neighbor's bromeliads are out of your jurisdiction. Three: your biters aren't container breeders at all: canal-origin Culex and no-see-ums off the Intracoastal never touched your treated water. That's the gap professional barrier treatment covers: a plant-based MPB blend plus a targeted control product applied to the vegetation where adult mosquitoes rest.
You Handle the Water. We Handle the Air.
Professional barrier treatment, 80%+ mosquito reduction by treatment 3–4. Kill, Mask, and Repel mechanism. FL License JB313837. Biweekly service, 7-day guarantee, no contracts.
After nearly two decades in corporate finance (most of it at Chico's FAS, where he oversaw operations and finance for 1,000+ retail locations across the US and Canada) Eric Vincent earned his MBA from Rollins College and made a deliberate pivot into pest control, completing his Pest Control Technology degree at the University of Florida while building Mosquito Shield of Boca and Fort Lauderdale from the ground up. He holds five Florida state licenses including Certified Pest Control Operator (JF341961) and Public Health licensee (PH340549), and is currently partnered with Arkion Life Sciences on next-generation all-natural mosquito control research.