Setting Up a Hospital Tank
How to set up a treatment tank: a separate, simple system where sick fish can be medicated without harming the display biofilter or sensitive tankmates.
Overview
A hospital tank is a separate system used to treat sick fish away from the main display. Treating in a dedicated tank protects the display: many medications damage the biological filter or harm invertebrates and sensitive fish. University of Florida IFAS guidance notes that bath treatments are not recommended in any system where treated water contacts the biological filter, because medications can kill or inhibit nitrifying bacteria.
Why a separate tank
- Keeps medication away from the display biofilter, which it can disable
- Protects invertebrates and scaleless or sensitive fish from drug exposure
- Concentrates treatment on affected fish at the correct dose
- Makes observation, water changes, and dosing easier
Bare-bottom design
A simple, easily cleaned setup is preferred. A bare bottom with no substrate makes it easy to siphon waste and uneaten food, and avoids gravel and rock that can bind or adsorb medications and complicate dosing. Provide simple shelter such as a clean plastic plant or a piece of inert pipe so the fish feels secure without adding surfaces that interfere with treatment.
Filtration during medication
The tank still needs filtration and stable water, but medications complicate biological filtration. Activated carbon must be removed during treatment because it adsorbs medication out of the water. Where a biofilter is used, be aware that some treatments can harm nitrifying bacteria; in practice many hospital tanks rely on frequent partial water changes plus a sponge filter, with close monitoring of ammonia and nitrite.
- Remove activated carbon before dosing — it strips medication from the water
- Use a simple sponge or seeded filter; expect possible biofilter impact from drugs
- Test ammonia and nitrite regularly, since the filter may be compromised
- Perform partial water changes to control waste and reset doses as directed
Monitoring during treatment
Because the biofilter may be weakened by medication, water quality can deteriorate quickly. Test ammonia, nitrite, and pH frequently and watch the fish for changes in breathing, colour, and behaviour. UF/IFAS stresses that correct diagnosis and dosing matter: under-dosing or stopping early can fail to clear the problem and, for antibiotics, promote resistance.
After treatment
Once the course is complete and the fish has recovered, restore normal filtration (including fresh activated carbon to remove residual medication if desired) and confirm stable, safe water before returning the fish to the display. Disinfect nets and equipment used in the hospital tank before they touch the main system.