Data and measurements from our catalog, checked against each manufacturer's spec sheet.
- Use distilled water with an additive or a premixed PC coolant; never tap water or car antifreeze.
- Clear coolant (colorless or tinted) needs the least maintenance and is the safest place to start.
- Pastel (opaque) and shimmer coolants look amazing in a fishbowl, but they get dirtier and need frequent cleaning.
- Don't mix coolant brands or types, and don't mix aluminum and copper in the same loop.
- Before turning on the PC, run the filled loop for 24 hours with only the pump to check for leaks.
1AIO or custom loop: where coolant comes in
An AIO (closed-loop liquid cooler) comes sealed from the factory: you don't refill it or choose its coolant, and it's what the configurator uses. A custom loop is built part by part (CPU or GPU block, radiator, pump, reservoir and tubing) and you pick and change the coolant. In a fishbowl case, with glass on two sides, the coolant is always on show, so its color is part of the design.
2Distilled water with an additive
The cheapest option and the one that cools best. The water must be distilled or deionized, never tap or mineral water: their salts leave deposits and cause corrosion. You add a PC additive or concentrate (a biocide against algae and bacteria plus a corrosion inhibitor) at the dose the maker recommends. It's completely clear, so the color comes from the tubing and lighting.
3Clear premixes (colorless or tinted)
Ready to pour, with biocide and inhibitor included, in colorless or tinted versions (red, blue, green, purple…). For example: Corsair Hydro X XL8, EK-CryoFuel Clear or Mayhems XT-1. They're the best choice for a first fishbowl build: they leave almost no residue and the tint adds color without the problems of opaque coolants. Under strong UV or LED light, some tints fade over the months.
4Pastel or opaque (solid colors)
They carry suspended particles that give a solid, matte color, like Mayhems Pastel or EK-CryoFuel Solid. Pastel white is the favorite for white fishbowl builds. The trade-off: the particles can settle if the PC sits off for a long time and they clog the fine channels in the blocks, so check the loop every few months and flush the parts well when you change it. They cool slightly less than clear coolants.
5Shimmer, pearl or UV-reactive
They carry micro-particles that swirl and shine as they flow (like Mayhems Aurora) or glow under UV light. They're the most eye-catching for photos and video, and also the most delicate: they settle, stain tubing and blocks, and need a full clean often. Only choose them if you accept that upkeep; for a daily-use PC, a tinted clear coolant is better.
6What you should never use
Tap water, mineral water, drinks or water with food coloring; car antifreeze or engine coolant, which corrodes and attacks seals and tubing; and mixes of coolants from different brands or types, which can react and turn into gel or sediment. Don't mix metals either: with an aluminum radiator and copper blocks, galvanic corrosion eats away at them. In PCs the norm is copper, brass and nickel throughout the loop.
7Tubing: hard or soft
Hard tubing (PETG or acrylic) is what showpiece fishbowl builds use: clean straight lines, but it has to be bent with heat and cut precisely. Soft tubing is easier and more forgiving; choose good quality, because cheap tubing leaches plasticizer that clouds the coolant. With pastel coolants, clear hard tubing shows off the color best.
8Filling, leak testing and maintenance
Fill the loop from the reservoir with the power supply disconnected from the motherboard and graphics card; a 24-pin jumper turns the PSU on to power only the pump. Run the pump for 24 hours with paper towels under every fitting: if they stay dry, you can connect the rest. Tilt the case gently to bleed out air bubbles.
As a rough guide, clear coolant is changed about once a year and pastel or shimmer every few months; always follow the coolant maker's advice and change it sooner if it looks cloudy, has sediment or stains.