* Waste Production: Goldfish are messy eaters and produce a lot of waste (ammonia and nitrates). Without a filter, these harmful substances build up in the water, poisoning the goldfish.
* Oxygen Depletion: Fish need oxygen to breathe. A filter helps aerate the water, ensuring there is enough dissolved oxygen for the goldfish.
* Water Quality: A filter helps maintain water clarity, removing debris and other contaminants. Poor water quality can lead to infections and diseases in goldfish.
Even a small goldfish needs a filter. If you are determined to keep a goldfish without a filter, you will need to:
* Do very frequent water changes: At least 25% of the water should be changed daily, and ideally, you should do a full water change every 1-2 days.
* Use a dechlorinator: Tap water contains chlorine that is harmful to fish.
* Monitor the water parameters: Use a test kit to check ammonia, nitrite, and nitrate levels regularly.
* Keep the tank small: A small tank will require even more frequent maintenance.
Important: This approach is extremely challenging and not ideal for the goldfish's health. It is much better to have a filter in place. A small, inexpensive filter is a much better investment for your goldfish's well-being.