Algaecide Dosing Calculator
Calculate exactly how much algaecide to add to your pool. Enter your pool volume and algaecide type to get the precise dose for weekly prevention, season opening, or treating an active algae outbreak.
Algaecide Type
Check your algaecide bottle label for the active ingredient percentage. Polyquat 60% is the most common residential choice — it's non-foaming and compatible with all sanitizers.
Treatment Purpose
Preventive doses are added weekly to stop algae before it starts. Use Initial/Opening at the start of the season. Use Outbreak dosing only when visible algae is present — follow up with shock and brushing.
The total water volume of your pool in gallons. Check your pool builder's paperwork, or estimate using: length × width × average depth × 7.48.
Algaecide to Add
Add directly to the pool with the pump running. For best results, pour around the perimeter rather than in one spot.
💡About this calculator▼
Getting the algaecide dose right matters — too little and algae comes back within days, too much wastes money and can cause foaming or staining. This calculator uses actual product label rates for each algaecide type to give you the correct amount for your pool size and situation.
The calculator looks up the standard dosing rate for your algaecide type and treatment purpose (in fluid ounces per 10,000 gallons), then scales it to your pool volume. Rates are based on real EPA-registered product labels for each algaecide class — not generic estimates.
📐How it's calculated▼
Amount (fl oz) = (Pool Volume ÷ 10,000) × Dose Rate
Dose rates per 10,000 gallons by product type:
• Polyquat 60%: 3 oz (prevention), 8 oz (initial/opening), 14 oz (outbreak)
• Polyquat 30%: 6 oz (prevention), 17 oz (initial/opening), 28 oz (outbreak)
• Quat 10%: 6 oz (prevention), 26 oz (initial/opening), 26 oz (outbreak)
• Copper-based: 1.5 oz (prevention), 8 oz (initial/opening), 16 oz (outbreak)
Rates derived from In The Swim Algaecide 60 Plus, In The Swim Algaecide 50, and BioGuard Banish product labels.
📎Source: EPA-registered product labels: In The Swim Algaecide 60 Plus, In The Swim Algaecide 50, BioGuard Banish
🔍Finding your inputs▼
Pool Volume: Check your pool builder's paperwork or equipment manual — most list the volume in gallons. If you don't have it, a rough estimate is length × width × average depth × 7.48 for a rectangular pool.
Algaecide Type: Check your bottle's active ingredients label. Polyquat products list "poly[oxyethylene...]" as the active ingredient at 30% or 60% — these are non-staining and non-foaming. Quat 10% products list a quaternary ammonium compound at ~10%. Copper-based products list copper sulfate or metallic copper.
Treatment Purpose: Choose Weekly Maintenance for routine prevention. Choose Opening/Initial at the start of the season. Choose Active Algae Outbreak only when you can see algae — combine with shock treatment and brushing.
⚠️Special situations▼
Copper-based algaecide with well water or high metal content
Copper algaecides can cause green or black staining on pool surfaces if your water already has high metal content. Test your water for metals first. If metals are elevated, use Polyquat instead — it's non-metallic and stain-free.
Active algae outbreak that doesn't clear after one treatment
If algae is still visible after 24 hours, the pool likely needs a second full outbreak dose. Brush all surfaces again, run the filter continuously, and repeat. Check that your chlorine and pH are in range — algaecide works best when chlorine is 1–3 ppm and pH is 7.2–7.6.
Pool with attached spa or water feature
Copper-based algaecides can stain spa jets, decorative fountains, and tile grout. Use Polyquat 60% for pools with attached features — it's specifically formulated to be safe for these applications.
Quat 10% causing foam
Quat algaecides foam when agitated — this is normal. The foam is harmless and will dissipate within a few hours. If foaming is excessive, you may have overdosed or your pool has high organic load. Polyquat products are non-foaming if foam is a persistent issue.
❓Common questions▼
What's the difference between Polyquat and Quat algaecides?
Polyquat (polymeric quaternary ammonium) algaecides are non-foaming, non-staining, and compatible with all sanitizer systems. They're the most popular choice for residential pools. Quat algaecides at 10% concentration are older-generation products that can cause foaming, especially at higher doses. Polyquat 60% is the most effective and hassle-free option for most pool owners.
Can I add algaecide and shock at the same time?
No — add shock first and wait at least 24 hours before adding algaecide. High chlorine levels from shock will break down many algaecide compounds before they can work. Shock kills most of the algae, then algaecide cleans up the rest and prevents regrowth.
How often should I add algaecide?
For prevention, once a week is standard — typically the same day each week after your regular pool maintenance routine. During hot weather, heavy use periods, or after heavy rain, consider dosing every 3–5 days since these conditions accelerate algae growth.
Why is the initial/opening dose so much higher than the maintenance dose?
Maintenance doses top off an existing chemical residual already present in the water. An initial dose has to establish that residual from scratch in water that contains none — which requires significantly more product. Using a maintenance dose for an opening treatment is one of the most common algaecide mistakes, leaving the pool unprotected in the first weeks of the season.
Is copper algaecide safe for vinyl liner pools?
Copper algaecide can stain vinyl liners if the pH is out of range or if the product is added undiluted. If you use copper algaecide in a vinyl liner pool, pre-dilute it in a bucket of pool water before adding, maintain pH between 7.4–7.6, and pour slowly around the perimeter rather than in one spot.