Aquarium Water Problems and How to Fix Them

Last updated: 1 November 2026

Clear answers to the most common water questions from aquarium keepers.

How often to change aquarium water

How often to change aquarium water depends on stocking, but most tanks do well with 20 to 30% weekly. Heavily stocked tanks may need more often, lightly stocked planted tanks less. Always treat new water with conditioner.

How to clean an aquarium

How to clean an aquarium: unplug equipment, scrape the glass, siphon waste from the substrate, change part of the water, and rinse filter media in old tank water, not tap water. Never clean everything at once, because you will remove helpful bacteria.

Why is my aquarium water cloudy

Why is my aquarium water cloudy? In new tanks it is usually a harmless bacterial bloom that clears in days. Other causes are overfeeding, fine substrate dust, a dirty filter or too many fish. Test ammonia and nitrite, reduce feeding, and do small water changes.

Green water in aquarium fix

For a green water in aquarium fix, reduce light to 6 hours, move the tank out of direct sun, do a water change, and add floating plants or a UV sterilizer. A short blackout can also help. Treat the cause, which is usually too much light and nutrients.

How to remove algae from aquarium

How to remove algae from aquarium glass and decor: scrape or brush it off by hand, trim affected leaves, and then fix the balance of light, nutrients and CO₂. Algae-eating shrimp and snails help but do not replace good balance.

Fish tank smell

A fish tank smell usually means decaying food, a dirty filter or dead plants or fish. A healthy tank smells earthy at most. Remove waste, clean the filter, do a water change and feed less.

Fish dying in new tank

Fish dying in new tank setups is commonly caused by ammonia and nitrite in an uncycled tank, chlorine in untreated water, rapid temperature changes or too many fish too soon. Test the water, do water changes, feed lightly, and cycle the tank before adding more fish.

Ammonia in aquarium

Ammonia in aquarium water is toxic. If your test shows ammonia, do a partial water change, treat with a conditioner that binds ammonia, reduce feeding and check the filter is working. Cycling prevents most ammonia problems.

How to lower aquarium pH

How to lower aquarium pH: first check that you need to, because stable pH matters more than the number. Safe methods include driftwood, blending with soft or RO water, and nutrient soil. Avoid pH-down chemicals that cause swings.

Aquarium water conditioner

An aquarium water conditioner removes chlorine and chloramine from tap water so it is safe for fish. Use it every time you add new water, and dose by the total volume you are treating.

Aquarium salt use

Aquarium salt use is occasional, not routine. It can help some freshwater fish during certain treatments, but many plants, shrimp and scaleless fish dislike salt. Follow dosage instructions and ask an expert before using it.

Using tap water in aquarium Bangladesh

Using tap water in aquarium Bangladesh tanks is common. Water quality differs by area, so test hardness and pH, and check for iron or other contaminants. Always use a conditioner to remove chlorine and chloramine. If your water source is unusual, ask us.

Remove chlorine from aquarium water

To remove chlorine from aquarium water, use a water conditioner. Letting water stand for 24 to 48 hours removes plain chlorine, but not chloramine, so a conditioner is more reliable.