FAQ: Grooming for fish

Siphoning stirs up fine particles of gravel and dirt. The filter usually catches them and the rest settle within a few hours. If the cloudiness lasts longer, check the filter and the water parameters.

Yes, partial water changes are normally done with the fish in the tank. Catching and moving them is more stressful than the change itself. Just work slowly and pour the new water gently so you do not create a strong current.

The exact time matters little; regularity matters more, such as the same day each week. It is handy to change water before feeding or a few hours after, and when you have time to watch the fish afterwards.

Yes. The filter traps dirt and turns ammonia into less harmful compounds, but nitrates and other substances still build up. Only regular partial water changes remove them.

Multiply the inside length, width and water height in centimetres and divide by 1000 to get litres. Gravel, rocks and decorations take up part of the volume, so the real amount of water is less than the tank's nominal size, which matters when dosing products.

Most important is that the magnet matches the glass thickness stated by the maker: too weak and it will not hold, too strong and it is hard to move. A larger cleaner is easier on a big tank, and a floating inner part does not sink to the bottom if it detaches.

Only one clearly made for acrylic with a soft, non-scratching pad. Acrylic is much softer than glass, so cleaners and blades made for glass scratch it easily.

Usually a grain of sand or gravel gets trapped between the cleaner and the glass and leaves scratches. Do not clean right down at the substrate, keep the inner part from dropping into the gravel, and rinse it before continuing if it does.

Floating models rise to the surface on their own; others have to be fished out by hand or pulled to the glass with the outer magnet. Before cleaning again, check and rinse the inner part so no gravel is left on it to scratch the glass.

A scraper with a blade is for hard, stuck-on green or chalky algae spots on glass. A sponge or scrubbing pad suits soft film and routine cleaning, but it will not remove firmly attached algae.

A glass tank can be cleaned with a metal blade held at a shallow angle and used carefully. It is not suitable for acrylic, which it scratches. Keep the blade away from the silicone seams so you do not cut the sealant.

Replace the blade when it dulls, chips or starts to rust, because it then cleans poorly and may scratch. Rinse and dry it after every use, especially if you use it in a marine tank.

Only a brand-new one that has never touched detergent, has no antibacterial treatment and is kept just for the tank. Some kitchen sponges are impregnated with chemicals, so a dedicated aquarium pad or cleaner is safer.

A narrow scraper, a soft brush or an old toothbrush kept only for the tank works well in corners. Do not scrape the silicone with sharp blades, as you may damage the seam and cause a leak.

Take the decoration out and scrub it with a brush in tank water or under hot water, with no detergent. Rocks and hard decorations can be scalded with hot water; let them cool before putting them back.

The commonest causes are lighting that is on too long or too strong, direct sunlight and excess nutrients from overfeeding or infrequent water changes. Fixing these causes usually reduces algae more than cleaning alone.

Around 8–10 hours of light a day is enough for most aquariums. Longer lighting encourages algae, and a timer helps keep a steady day and night rhythm that also benefits the fish.

Better not. Direct sunlight encourages algae and can overheat the water in summer, while in winter the water cools more by the window. Choose a spot out of direct sun and away from radiators.

A small amount of algae is natural and usually harmless. Heavy growth spoils the view, can smother plants and uses up oxygen at night. A sudden algae bloom usually means the tank has too much light or too many nutrients.

Green water is caused by microscopic algae floating in the water, usually because of too much light and nutrients. Shorter lighting, moderate feeding and regular water changes help, and some aquarists use a UV steriliser.