FAQ: Water Care for fish

Bettas like warm, calm, soft to moderately hard, slightly acidic to neutral water. Above all it must be clean, free of ammonia and nitrite, conditioned and at a stable temperature, and leaves or driftwood add a comfortable setting.

Goldfish adapt well to moderately hard, neutral to slightly alkaline water, so conditioned tap water often suits them. Most important for them are plenty of water, a strong filter and frequent changes, as they produce a lot of waste.

Livebearers mostly prefer moderately hard to hard, neutral to slightly alkaline water, so Lithuanian tap water usually suits them. Mollies are sometimes kept with a little salt, but it is not necessary if the water is hard.

Discus need warm, soft, slightly acidic and very clean water, so an RO and tap water mix is often used. They are sensitive to nitrate and organics, so water is changed often and in large amounts with well-prepared new water.

Used as directed, aquarium fertilisers are usually safe for fish. Copper in some fertilisers or overdosing can harm shrimp, so choose fertilisers the manufacturer states are invertebrate-safe and do not overdose.

They are liquids that add vitamins, iodine or trace elements to the water, for example after water changes or stress. They can be useful, but a varied diet and regular water changes usually supply most of what is needed.

Conditioner, bacteria starter and fertiliser can usually be used together, but not every product combines well; for example some algae treatments or medications disrupt bacteria. Read every product's instructions and do not overdose.

Some medications can harm filter bacteria, plants or invertebrates and lower oxygen levels. During treatment increase aeration, take carbon out of the filter if the instructions require it, test ammonia and nitrite and follow your vet's advice.

After treatment, several partial water changes are usually done and activated carbon is added to the filter, which absorbs many medications. Special resins are used to remove some substances, such as copper, so follow the medication's instructions.

Most conditioners and bacteria starters are harmless to snails, but some algae treatments and medications, especially copper-based ones, can be deadly to them. Before using a new product in a tank with snails or shrimp, check it is suitable for invertebrates.

Thin, pitted or crumbling shells often point to water that is too soft or acidic and short of calcium. Test pH, GH and KH, and if needed raise hardness with mineral products or calcium sources made for aquariums.

Failed moults are often linked to unsuitable or suddenly changed hardness, a lack of minerals or overly large water changes. Change smaller amounts, match the new water's parameters and keep GH suitable for the shrimp species.

They are remineralisers for preparing RO water for shrimp. GH+ salts add calcium and magnesium without carbonates, suiting Caridina shrimp, while GH/KH+ also adds carbonates, suiting Neocaridina and other harder-water species.

Axolotls like cool water, around 16–20 °C, that is clean, neutral to slightly alkaline, moderately hard and free of chlorine. They are sensitive to ammonia and heat, so regular water changes and a cool spot matter, and salt or medication is not used without a vet's advice.

Turtle water should be dechlorinated, clean and at the right temperature, with ammonia and nitrite monitored as in a fish tank. Since turtles are very messy, a powerful filter, frequent changes and feeding in a separate container so leftovers do not stay in the tank all help.

Multiply the tank's length, width and water height in centimetres and divide by 1000 to get litres. Substrate and decor take up some space, so the actual water volume is roughly 10–20% less, and dose products according to that.

Mg/l means milligrams per litre and ppm parts per million, and for water the two are practically the same. Hardness is also often given in German degrees (°dH), so when comparing advice, note which units it uses.

Common mistakes are adding fish to an uncycled tank, overfeeding, rinsing the filter in tap water, forgetting conditioner and changing too much water at once. Regular testing and small, consistent changes help avoid them.

Yes, conditioners, bacteria starters and other products have expiry dates, and opened bottles can lose effectiveness over time. This matters most for bacteria starters, so buy a pack size you will use within a reasonable time.

Keep them in their original packaging, tightly closed, in a cool, dark place out of reach of children and pets. Do not decant them into food or drink containers, and wash your hands after use, especially with medications or pH products.