Aquarium Additive Doser

Enter your tank's total water volume (in gallons or liters), then input the dosage rate from your product label (ml per gallon). The calculator instantly shows the total amount you need. You can also select a preset from popular brands like Seachem and API, or use the reference table to quickly apply known dosages. For reverse calculation, switch to "Total → Dose" mode to find out your current ml-per-gallon rate based on how much you've been adding.

"ml per gallon" (milliliters per gallon) is the standard way aquarium product manufacturers express dosage rates. It tells you how many milliliters of additive to use for each gallon of tank water. For example, Seachem Prime recommends 0.1 ml per gallon (which equals 5 ml per 50 gallons). Understanding this ratio helps you scale doses accurately for any tank size — especially nano tanks or large systems where the standard instructions may not directly apply.

This calculator uses US gallons (1 US gal = 3.785 liters), which is the standard for most aquarium products sold in North America. If you're in the UK and your product label uses UK imperial gallons (1 UK gal = 4.546 liters), switch the unit selector to "liters" for the most accurate result. The difference is significant: a 50 UK gallon tank holds about 227 liters, while a 50 US gallon tank holds about 189 liters — a 20% difference that can lead to underdosing or overdosing if not accounted for.

For doses under 1 ml, use a 1ml syringe or a calibrated dropper/pipette — these are inexpensive and available at most pharmacies or aquarium shops. As a rough guide, 1 ml ≈ 20 drops for water-based solutions (though viscosity affects drop size). For nano tanks under 5 gallons, even a syringe may be imprecise; consider pre-diluting the additive in distilled water and dosing from the diluted solution. Never eyeball small doses — overdosing plant fertilizers like Excel or iron supplements can harm livestock.

Generally, no — most manufacturers recommend dosing additives separately, at least 10–15 minutes apart. Some products can react with each other (e.g., dechlorinators like Prime can neutralize certain medications). Always read the product label for compatibility information. If you need to dose multiple products on the same day, calculate each dose individually using this tool and add them to the tank one at a time with adequate mixing in between.

Overdosing can range from mild to severe depending on the product. Dechlorinators (like Prime) are relatively safe at moderate overdoses but can deplete oxygen at extreme levels. Liquid carbon supplements (like Excel) are toxic in high doses and can kill fish and invertebrates. Iron and trace fertilizers can trigger algae blooms or poison sensitive shrimp. pH adjusters can cause dangerous pH swings. If you suspect an overdose, perform an immediate partial water change (25–50%) and monitor livestock closely. Always double-check your calculations — that's exactly what this tool helps prevent.

Dosing frequency depends on the product and your tank's needs. Comprehensive fertilizers (like Flourish) are typically dosed 1–2 times per week. Dechlorinators are used only during water changes. Bacteria starters (like Stability) follow a 7-day initial cycle, then as needed. Carbon supplements (like Excel) may be dosed daily or every other day. Always follow the manufacturer's schedule, but adjust based on plant health, algae levels, and water test results. Use this calculator each time to ensure your dose matches your actual water volume.

This is completely normal! Products designed for typical aquariums (20–75 gallons) often require tiny amounts for nano tanks under 10 gallons. For instance, a 5-gallon tank using Seachem Flourish Comprehensive needs only ~0.42 ml — less than half a milliliter. This is why accurate measurement tools like 1ml syringes are essential for nano tank keepers. Our calculator displays drop equivalents (≈20 drops/ml) and shows a special warning for doses under 1 ml to remind you to use precise measuring instruments.