Medication dosing
Calculate the right dose for common aquarium medications, with species warnings based on your stocking.
Manual overrides
By default the calculator reads your saved stocking roster (if you've used the stocking calc) to surface species-specific cautions. If you don't have a saved roster, or want to ignore it for this calculation, toggle the override here.
What this does
Pick a medication, enter your tank volume, and the calculator gives you the exact dose along with re-dose schedule, water-change schedule, and carbon-removal advice.
The differentiating feature: if you've used the stocking calculator on this site, your roster is saved. The medication calc reads that roster and surfaces specific cautions for what's in your tank. Treating ich with Ich-X and you have shrimp? The shrimp warning is highlighted, not buried.
What's in the database
Eight of the most common aquarium medications, covering the situations most fishkeepers actually face:
- PraziPro (Hikari): flukes, tapeworms, internal parasites. Shrimp-safe.
- API General Cure: internal parasites (Hex disease), flukes. Powdered combination of metronidazole and praziquantel.
- Ich-X (Hikari): ich / white spot. The standard treatment. Kills shrimp and most snails; halve the dose for scaleless fish.
- ParaGuard (Seachem): broad-spectrum external parasites and fungal infections. Gentler than ich-x but still kills invertebrates.
- KanaPlex (Seachem): gram-negative bacterial infections, fin rot, dropsy. One of the few antibiotics that works in planted shrimp tanks.
- API Erythromycin: gram-positive bacteria and cyanobacteria. Most commonly used to clear blue-green algae in planted tanks.
- Furan-2 (API): broad-spectrum bacterial and fungal. Stains plants and silicone yellow-green; this clears with water changes after treatment.
- Aquarium salt: mild external parasites, stress relief, ich assist. Overrecommended online; kills shrimp and harms scaleless fish.
What the cautions actually mean
Scaleless fish are species without conventional scales: catfish (cories, plecos, otocinclus), loaches (kuhli, clown, hillstream, weather, yoyo), eels, and similar. They absorb medications faster than scaled fish, so they need reduced doses or alternative treatments. The big offender is malachite green (the active ingredient in Ich-X) which can be fatal to scaleless fish at full strength.
Shrimp are invertebrates and react badly to most fish medications. Copper-based treatments kill them instantly. Aldehyde-based treatments (ParaGuard, formalin) kill them within hours to days. Praziquantel is one of the few that's genuinely shrimp-safe.
Snails are similar to shrimp but more variable. Most snails survive aldehyde treatments at low dose but die at full dose. Mystery snails and nerites are more sensitive than ramshorns or MTS.
Biofilter suppression matters for antibiotics. Kanaplex and Erythromycin can knock down nitrifying bacteria, causing ammonia and nitrite spikes during and after treatment. Test parameters daily during the dosing course and for a week after.
Why remove carbon
Activated carbon absorbs organic molecules, including most medications. If you dose into a tank with carbon running, the carbon removes the medication faster than the fish can absorb it, neutralising the treatment. Pull the carbon cartridge before dosing and put it back after the treatment cycle completes (or replace it; carbon doesn't desorb meds back into the water).
Why re-dose
Most parasites and bacteria have life cycles where some life stages are immune to the medication. Praziquantel kills adult flukes but not the eggs; you re-dose after the eggs hatch. Ich treatments need to continue through the free-swimming theront stage, which only emerges from cysts under the substrate, so the treatment runs longer than the visible spots persist.
Stopping treatment when fish look better is the most common reason treatments fail. Run the full course.
When to call a vet
The calculator handles standard dosing. It doesn't handle: dropsy, advanced bacterial septicemia, suspected mycobacterium, parasites that don't respond to standard treatment, anything with neurological symptoms. If your fish has a problem you can't identify confidently, a fish vet (yes, they exist; check the AquaVet directory or your local exotics vet) is worth more than experimenting with medications.