Why does my Goldfish keeps opening mouth at top of tank?

It sounds like your goldfish might be experiencing gasping for air. This is a common issue with goldfish, and it can be caused by several factors:

1. Low Oxygen Levels:

* Overcrowding: Too many fish in the tank can deplete oxygen levels.

* Insufficient Filtration: A filter that is too small or not working properly can lead to poor water quality and low oxygen.

* Algae Overgrowth: Algae can block sunlight and hinder oxygen production by plants.

* High Water Temperature: Warmer water holds less dissolved oxygen.

* Low Water Flow: Still water doesn't allow for enough oxygen absorption.

2. Other Health Issues:

* Gill Problems: Parasites, infections, or injuries can affect the gills' ability to absorb oxygen.

* Swim Bladder Issues: A malfunctioning swim bladder can make it difficult for the fish to stay at the surface, causing it to gasp.

* Constipation: Constipation can put pressure on the swim bladder, leading to gasping.

Here's what you can do:

1. Assess the tank environment:

* Overcrowding: Do you have too many fish in the tank? If so, consider rehoming some or getting a larger tank.

* Filtration: Is your filter large enough for the tank size and fish load? Is it running properly?

* Algae: Is there excessive algae growth in the tank? Clean it up and consider adding more plants.

* Water Temperature: Is the water temperature too high? Aim for 68-72°F (20-22°C) for goldfish.

* Water Flow: Does the water have adequate flow? Add an airstone or increase the filter flow.

2. Observe for other symptoms:

* Lethargy: Does the fish seem sluggish or inactive?

* Loss of Appetite: Is the fish eating less than usual?

* Redness or Swelling: Are there any signs of redness or swelling around the gills or mouth?

3. Seek professional help:

* If the gasping persists despite addressing the environmental factors, it's best to consult a veterinarian who specializes in aquatic animals. They can diagnose any underlying health issues and recommend appropriate treatment.

Remember: Gasping for air is a serious sign in goldfish. It's essential to act quickly to address the problem and improve the fish's chances of survival.