My Notes on Goldfish: Not Just a Fish in a Bowl

Like many of you, my first fish was a Goldfish. I won it at a funfair (or maybe bought it for RM2 at a shop). I put it in a small round bowl, fed it some flakes, and wondered why it died a few weeks later.

I used to think I was just “bad luck” with fish. Years later, I learned the truth: Goldfish are actually heavy-duty animals. They are not delicate flowers; they are biological machines that eat a lot, poop a lot, and grow huge.

Here is what I wish I knew back then.

1. History: The Accidental Beauty

Goldfish (Carassius auratus) are actually just shiny Carp. Over 1,000 years ago in ancient China, people noticed that some silver carp had genetic mutations that made them gold or red. They started breeding these mutants in ponds.

Over centuries, they bred them into two main groups:

The Slim Ones: (Comet, Common) – Built for speed.
The Round Ones: (Fancy Goldfish) – Built for looks.

2. The Varieties (Know What You Buy)

In Malaysian shops, you usually see mixed tanks. But you need to know the difference because they cannot live together.

Single-Tail (Comet / Shubunkin):
- The Look: Long body, short fins. They swim very fast.
- The Trap: They look small in the shop, but they grow to 12 inches (30cm). They belong in a pond, not a tank. If you put them with slow fish, they will eat all the food before the others get a bite.
Fancy Goldfish (The “Cute” Ones):
- The Look: Round bodies, double tails, sometimes wobbly heads.
- Popular Types: Oranda (has a “brain” growth on head), Ranchu (no dorsal fin, looks like an egg), and Ryukin (has a humpback).
- My Preference: I love Ranchus. They swim awkwardly and look like swimming potatoes.

3. The “Bowl” Myth

This is the hardest thing to tell new owners. Goldfish do not belong in bowls.

The Size Issue: Even the “cute” round ones grow to the size of a grapefruit.
The Oxygen Issue: Bowls have very little surface area. Goldfish need a lot of oxygen because they are messy eaters.
The “Stunted” Myth: People say, “They only grow to the size of the tank.” This is technically true, but it’s painful. Their body stops growing, but their internal organs keep growing until they are crushed.
My Rule: One fancy goldfish needs about 75 Liters (20 Gallons) of water.

4. Personality: The Water Pig

Why do people keep them if they are so messy? Because they act like dogs.

Food Begging: Every time I walk past the tank, they wiggle at the glass like they haven’t eaten in weeks.
Hand Feeding: They are very gentle. You can train them to eat pellets right out of your fingers.
Scavenging: They spend all day pecking at the gravel (substrate). It’s quite relaxing to watch them work.

5. The Environment (The Filtration Challenge)

Goldfish have no stomach. They have a long intestine that processes food quickly. This means they produce a lot of waste.

Filtration: You need a filter rated for double your tank size. If you have a 100L tank, get a filter for a 200L tank.
Plants: Be careful. Goldfish are herbivores. They will eat your expensive plants. I only keep them with tough plants like Anubias or Java Fern because the leaves are too hard to chew.

6. Diet & The “Floaty” Problem

Have you ever seen a goldfish floating upside down? It’s heartbreaking. This is usually Swim Bladder Disease, caused by constipation and swallowing air.

My Fix: I avoid floating flakes. I use sinking pellets (like Hikari Lionhead) so they don’t gulp air at the surface.
The Magic Veggie: Once a week, I feed them boiled peas (skin removed). It acts like a laxative and clears out their system.

Goldfish are not a “throwaway” pet. They can live for 10 to 15 years. If you are willing to do the big water changes and buy a big filter, they are the most cheerful, friendly fish you can own. Just don’t expect them to stay small!