The short answer
A cold water tank is set up almost exactly like a tropical one, minus the heater. You still need a tank, filter, light, substrate, dechlorinator and a test kit — you just run it at room temperature and stock it with hardy, cool-water species. The most important step is the same as any aquarium: cycle it for several weeks before adding fish.
What “cold water” actually means
Cold water simply means no added heat — the tank sits at whatever your room does, usually 18–22°C. Good beginner choices are white cloud mountain minnows, which thrive in a nano tank, and small shrimp or snails. Goldfish are also cold water, but they get large and produce a lot of waste, so they belong in a big tank (75 litres and up), never a bowl. Avoid tropical fish here — they need stable warmth.
Setting it up, step by step
- Rinse your substrate and add it, then hardscape and any plants.
- Fill with dechlorinated water and install the filter and light.
- Run everything and start the nitrogen cycle — this is the slow part.
Cycling and stocking
Even without a heater, your filter still needs beneficial bacteria to process fish waste. Follow our full setup walkthrough and cycling guide before adding livestock. Once the cycle is done, add fish slowly — see how long it takes to set up an aquarium.
For hardware, browse our aquariums and filter hubs, and if you’re new, start with the best beginner aquarium.