The short answer
A hospital tank is a simple, bare, cycled tank kept for treating and observing sick fish away from your main community. It doesn’t need decor or a fancy setup — just a heater, a gentle sponge filter, stable water matched to your display tank, and somewhere for the fish to hide. Keep it easy to clean, and always check water parameters before considering any treatment.
What you need
Keep it minimal and functional:
- A bare-bottom tank — no substrate makes waste easy to spot and remove.
- A heater to hold a steady temperature.
- A sponge filter — gentle and safe if you later medicate (unlike carbon-based media, which can remove medication).
- A simple hiding spot such as a plant pot or artificial plant to lower stress.
- A lid, and dim lighting.
Skip gravel, bright lights and heavy decor — they only make cleaning and observation harder.
Using it well
When you move a fish in, match the water and acclimatise slowly so the transfer itself doesn’t add stress — the same careful approach as how to acclimate new fish. Then observe and test before you treat: many problems ease with clean, warm, stable water alone. If medication is genuinely needed, research the right product for the condition and species, and ask a vet or experienced keeper before dosing. Because the volume is small, do smaller, more frequent water changes to keep it pristine.
This is general setup guidance, not a diagnosis or treatment plan.
Between uses
Clean and dry the tank and equipment between patients, and never share nets or tools with your display tank without disinfecting. The same tank doubles as quarantine for new fish — see how do I quarantine a sick fish? and do I need to quarantine new fish?