FAQ: Supplies for fish

Snails help graze some of the film off the glass and decor, but they do not remove the causes of algae – too much light and excess nutrients. They complement regular care but do not replace it.

A shrimp tank needs stable, well-established water, a gentle filter with a guard on the intake and plenty of plants or moss. A sponge filter is often used so the young are not sucked in.

Besides shrimp and snails, crayfish, crabs and mussels are kept in freshwater tanks. Crayfish and some crabs can catch fish or eat plants, and crabs often need a land area too.

Crayfish often catch slow fish or fish sleeping on the bottom at night and cut up plants, so they are better kept separately. Some dwarf crayfish species are calmer, but they also need hiding places, especially after moulting.

Small, less active species suit a nano tank, for example dwarf rasboras, Endler’s guppies or pygmy corydoras. Fast swimmers or larger fish, even when young, are too cramped in a small tank.

Some species, such as a betta or certain large cichlids, can live alone. For shoaling fish loneliness causes stress, so before buying check whether the species is social.

First find out your water’s hardness and pH – you can test them or ask your water supplier. Choosing species that suit your water saves you from constantly adjusting parameters.

A fish pond must be deep enough not to freeze to the bottom in winter and needs a filter and a pump. Choose a spot that gets shade for part of the day, away from trees whose leaves fall into the water.

For fish to overwinter safely, at least part of the pond is often recommended to be 1–1.5 m deep or more. At that depth the water does not freeze in winter and stays around 4 °C at the bottom.

A liner lets you build a pond of any shape and size, while a rigid preformed shell is easier to install but small and limited in shape. Choose a liner made for ponds and lay a protective geotextile underlay beneath it.

A filter is strongly recommended for most fish ponds, especially with koi or many goldfish. A filter with a UV lamp helps prevent green water, and a pump keeps the water moving and oxygenated.

It is often recommended that the pump moves at least half to all of the pond’s volume per hour, and more with koi. Also allow for the height the water is lifted, for example to a waterfall, as this affects the actual flow.

Green water is caused by tiny free-floating algae that multiply with sunlight and excess nutrients. A UV clarifier, water plants that shade the surface and moderate feeding all help.

In Lithuanian conditions ponds most often hold goldfish, koi, orfe and tench. Goldfish suit smaller ponds better, because koi grow large and need a lot of space.

It depends on the volume, depth and filter: koi need far more water than goldfish. Start with a small number, because pond fish grow and breed, and water quality quickly declines in an overstocked pond.

Fish spend the winter in the deepest part of the pond with their metabolism slowed down. In autumn remove leaves and sludge, reduce feeding, and in winter keep a hole in the ice so gases can escape.

Gases from rotting organic matter build up under the ice and can poison the fish. A foam float, an air pump or a pond heater helps keep a hole open; do not break the ice, as the shock waves harm the fish.

If the pond is shallow and freezes to the bottom, the fish can overwinter in a cool room in a large container or tank with a filter. The water should be cool, and the temperature must be changed gradually.

In spring clear out accumulated leaves and sludge, check the pump and filter, switch on the UV clarifier and change some of the water. Start the filter early so the bacteria recover before the fish begin feeding actively.

You can stretch a net over the pond, leave deep areas and hiding places, and make the edges steep so predators struggle to reach the water. Some people also use motion-activated water sprayers.