eSHa gdex Dosing: The Standard Five-Day Plan
By Richard James · Updated 27 October 2026
Checked against eSHa’s live calculator on 27 October 2026.
gdex is intended for specified flatworm infections, including skin/gill flukes and tapeworms. Irritation or heavy breathing alone does not establish that diagnosis. This page explains the standard calculation rather than choosing a medicine for an unexplained symptom.
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The standard plan at 100 litres
| Day | Amount or action |
|---|---|
| 1 | 100 drops / 3.2 mL |
| 2 | 50 drops / 1.6 mL |
| 3 | 50 drops / 1.6 mL |
| 4 | No dose |
| 5 | 50% water change |
This is the output of the manufacturer’s current standard calculator, not a requirement to add medicine on every day of a five-day plan. Use the leaflet for your bottle if it differs, and obtain clarification from eSHa before proceeding.
Scale each dose, not the water-change percentage
At 50 L, the three dosing days become 50, 25 and 25 drops. The day-five instruction remains a 50% water change. At 10 US gallons, the calculator converts to approximately 37.854 L and displays 38, 19 and 19 whole drops.
Our old entry incorrectly gave 20 drops per 100 L as one dose and suggested a generic repeat after seven days. It has been replaced. The standard course and a repeat course must not be collapsed into one instruction.
gdex has its own drop size
eSHa specifies 100 gdex drops as 3.2 mL. Do not use a generic 20-drops-per-mL conversion. The result page now provides the mL equivalent before whole-drop rounding. Choose one measuring method; the mL number is not an extra amount to add.
For small volumes, the displayed whole-drop amount and unrounded mL equivalent can differ. A 5 L example gives 3 rounded drops or 0.08 mL on day two. Use suitable measuring equipment and check the applicable label. Our minimum-volume software warning is not a guarantee of safety above its cut-off.
Repeat courses and livestock compatibility
Persistent infections may have separate instructions. The calculator shows the standard course only; it does not diagnose the parasite, decide on extensions or approve a combination. Read the full product guidance before choosing another course.
Check the specific animals, system and equipment against eSHa’s warnings. Marine use is limited to fish in quarantine systems; do not treat that as permission for general reef use.
Sources and tools
- eSHa gdex: current calculator, treatment information and precautions
- Our volume, conversion and rounding method
- Checking combinations and separate schedules
Written by Richard James
Aquarist, author, and creator of ShrimpKeeper.co.uk. Helping hobbyists achieve professional results through precision dosing.
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