Setting Up a Hospital Tank
Why You Need One and How to Use It Effectively
Introduction
A hospital tank is a separate, temporary aquarium used to isolate and treat sick fish away from the main display tank. It is one of the most important pieces of equipment a serious fishkeeper can have, yet it is also one of the most commonly skipped, usually until the moment you desperately wish you had one.
Treating fish directly in the display tank has serious drawbacks: medications can harm invertebrates, kill beneficial bacteria, stain silicone, and damage live plants. Many medications are also significantly less effective in a heavily planted tank with organic matter competing with the active ingredient. A hospital tank solves all of these problems and gives you far better control over the treatment environment.
Quick Overview
Setting Up the Hospital Tank
A hospital tank does not need to be elaborate. Its purpose is function, not aesthetics. What it does need is:
- A 10-20 gallon tank: large enough to comfortably house the sick fish and dilute medication, small enough to heat and treat economically
- A cycled sponge filter: keep a sponge filter running in your display tank permanently so it is always seeded and ready. This is the single most important preparation step.
- A heater: set to match or slightly exceed the display tank temperature; some diseases (ich in particular) progress and resolve faster at elevated temperatures
- A few hiding spots: PVC pipe elbows, ceramic caves, or a terracotta pot; sick fish need to feel secure to recover
- A lid: sick and stressed fish jump more than healthy ones
Bare bottom is preferred over substrate in a hospital tank: it makes cleaning easier, prevents medication from binding to substrate, and allows you to see any expelled parasites, shed skin, or abnormal waste that gives diagnostic information.
Moving a Sick Fish to the Hospital Tank
Act quickly once you decide a fish needs isolation. A fish that is visibly sick has often been deteriorating for longer than its visible symptoms suggest, and delayed treatment significantly worsens outcomes.
- Fill the hospital tank with water from the display tank to minimize osmotic shock during transfer
- Net gently and transfer quickly; prolonged netting attempts stress the fish further
- Match heater temperature to the display tank before transferring; do not move a tropical fish into cold water
- Dim or turn off lights for the first few hours to reduce stress
Medicating in the Hospital Tank
The hospital tank is where all medication happens. This protects your display tank and allows you to control the treatment precisely.
- Remove activated carbon: carbon adsorbs medication out of the water within hours, rendering treatment ineffective. Remove carbon from the filter before adding any medication.
- Follow dosing instructions exactly: underdosing creates ineffective treatment and can promote resistance; overdosing can harm the fish
- Complete the full course: stopping early when fish look better is a common mistake; many diseases appear to resolve before the pathogen is fully eliminated
- Perform water changes during treatment: check medication instructions; some require a water change between doses, others do not. Maintain water quality throughout.
Keep a basic medication kit stocked and ready before you ever need it. The worst time to discover you need ich medication is at 10pm on a Sunday when your fish is suffering. At minimum: an ich treatment, a broad-spectrum antibiotic (Kanaplex), Prazipro (for parasites), and Seachem Prime for emergencies.
After Treatment
Once treatment is complete and the fish has been symptom-free for at least one week, it is ready to return to the display tank. Perform a partial water change in the hospital tank to begin reducing medication concentration, then net the fish back to the main tank.
Break down and clean the hospital tank after use. Rinse all equipment in hot water (no soap), and store dry. The sponge filter should return to the display tank immediately to stay seeded for next time.