Skip to main content
Free Care Guides · Ages 7–10

Aquarium Basics

Eight things every fish wishes you already knew.

Fish are living creatures. The aquarium is their entire world. Everything that happens to that world — the temperature, the cleanliness, the oxygen, the food — happens to them. There is no going outside for a walk. There is no opening a window. There is no popping to the kitchen for a glass of water. The water is the kitchen. The water is the garden. The water is the air.

Yechiel has been keeping fish for forty-nine years. He asked the residents of his farm to explain his eight rules — because, as he put it, “perhaps hearing it from the fish themselves will finally make it stick.”

The fish agreed to help. Some of them were more enthusiastic than others. George, for example, had a great deal to say and none of it was polite. We have included it anyway. It is also correct.

“I've been doing this for fifty years. I know what's going on.”

— Yechiel Kuperman, Marine Biologist, standing by the tank with his tea

The eight guides

Part 01Oxygen and Water MovementTold by Ozzie the Oxygen BubblePart 02TemperatureTold by Empress Matilda, Dor 70Part 03Waste and AmmoniaTold by George the Cranky GuppyPart 04The Filter — a System of LifeTold by Professor NitraPart 05Feeding — Less Than You ThinkTold by Plecy the Glutton PlecostomusPart 06How Many Fish?Told by Turbo the Zebra DanioPart 07New Fish and AcclimationTold by Madame Molly — the PeacekeeperPart 08Warning SignsTold by Captain Cory — Cleanup Sergeant

The Eight Golden Rules

From Yechiel's notebook.

  1. 01Good water, stable water. Everything else depends on this. Clean, well-filtered, right temperature, and moving.
  2. 02Enough oxygen. Moving water brings oxygen. Still water loses it. Keep the filter and aeration running.
  3. 03The right temperature — keep it steady. Know what your fish needs. Then give it that, consistently, without sudden changes.
  4. 04A working filter — treat it gently. The bacteria in there are doing the most important work in the tank. Don't kill them by accident.
  5. 05Feed carefully. Less than you think. Uneaten food is pollution. Feed what disappears quickly, and stop.
  6. 06Don't overcrowd. More fish, more problems. Give them space and a filter that can keep up.
  7. 07Acclimate slowly. Every new fish deserves a gentle welcome. Float, drip, adjust. Never just pour.
  8. 08Pay attention. The fish will show you when something is wrong. Look at them every day. Learn their normal.

“This water has opinions. I suggest you listen to them.”

— George

📄 Prefer to print?

Download all nine guides as one printable PDF booklet.

Download the booklet

🎮 Now practise it

Rule 07 is acclimate slowly. Try it for real in our free game — drip a fish's new water in gently and read how they feel.

▶ Play “Take It Slow”