FAQ: Supplies for fish

Many cichlids, some barbs such as tiger barbs, and male bettas towards each other are considered more aggressive. That does not mean they cannot be kept, but tankmates and tank size must be chosen carefully.

No, two male bettas usually fight until one is injured. Keep a male on his own or with calm, short-finned tankmates, and use dividers only temporarily.

It is a tank where several peaceful species with similar needs are kept together, for example tetras, rasboras, corydoras and livebearers. It suits beginners if the species are chosen with care.

Livebearers such as guppies, mollies and platies give birth to free-swimming young and breed very easily. Egg-layers spawn eggs, and raising their fry often needs a separate tank and more effort.

You can keep only one sex, leave dense plants and let other fish naturally limit the fry numbers, or give the surplus to other fishkeepers. The tank should not become overcrowded, as water quality suffers.

Fish are usually transported in a bag with water and air. In the cold season protect the bag from the cold, on a hot day from the sun, and go straight home so the water does not cool down or overheat.

Float the bag in the tank for 15–20 minutes so the temperature evens out, then add a little tank water to it in several steps. Move the fish with a net and avoid pouring the shop water into your tank.

Experienced fishkeepers keep new fish in a separate quarantine tank for a few weeks to spot disease before adding them to the other fish. This is especially useful if the main tank already holds valuable or sensitive species.

Size depends a lot on the species: neons grow only a few centimetres, while some pleco catfish or larger cichlids get many times bigger. Before buying a young fish, check its adult size so it does not outgrow the tank.

Small fish such as guppies usually live 2–3 years, bettas 3–5, while goldfish and koi can live more than a decade in good conditions. Good water quality and suitable food extend their lives.

Yes, if their temperature, hardness and pH needs match and their temperaments are compatible. Biotope tanks with species from a single region are attractive but not required.

Usually not. Goldfish prefer cooler water and tropical fish warmer, and goldfish also produce a lot of waste and can eat small fish.

Coldwater species can live at room temperature without a heater: goldfish, White Cloud Mountain minnows and some danios. The room should not be too cold and the temperature should not fluctuate much.

Round-bodied fancy goldfish such as veiltails or orandas swim more slowly and are more delicate, so they need gentle flow and slow tankmates. Common, long-bodied goldfish are hardier and even suit ponds.

Goldfish eat a lot and produce a lot of waste, so the water gets dirty quickly. They need a filter rated for a larger volume than the tank and regular partial water changes.

Dwarf shrimp such as red Neocaridina and the larger, algae-eating Amano shrimp often suit beginners. They need a stable, established tank with no copper-based products.

Yes, with small, peaceful fish such as rasboras or small tetras. Larger fish, bettas or cichlids often eat shrimp and especially their young, so shrimp need plenty of hiding places.

Shrimp and snails are very sensitive to copper, which can be found in some medications, fertilisers or old pipes. Before using any product in a tank with invertebrates, check the label to see whether it is safe for them.

Nerite snails, which eat algae and do not breed in fresh water, are popular, as are mystery snails and ramshorns. Some small snails breed very fast, especially when the fish are overfed.

The most common cause is too much food, so first cut back on feeding. Snails can be picked out by hand or with traps, and chemical snail treatments should be used with care because they also harm shrimp.