FAQ: Plants for fish

Some rotala, ludwigia, alternanthera, red tiger lotus and certain Amazon swords have red shades. Most of them need strong lighting, iron fertiliser and often CO2 to bring out the colour.

Red plants usually turn green when they lack light or iron, or when they get too much nitrogen. Stronger lighting, iron fertiliser and CO2 usually help bring the red colour back.

Stem plants grow a long stem with leaves along it, such as hygrophila, rotala or ludwigia. They are planted a few stems together, grow quickly and are propagated by replanting cut tops.

Rosette plants grow their leaves from a single centre at the substrate, such as cryptocorynes, Amazon swords or vallisneria. They feed heavily through the roots, so a nutrient-rich substrate or root tabs matter to them.

Epiphytes are plants that grow attached to rocks or wood rather than rooted in the substrate, such as anubias, Java fern, bucephalandra and mosses. They do not need a nutrient substrate and take their food from the water.

Yes, for example tiger lotus or aponogeton, which are sold as tubers or bulbs. Press the bulb only partly into the substrate; some aponogetons go dormant after flowering and drop their leaves for a while.

Floating plants such as salvinia, duckweed or water lettuce absorb nitrates very quickly, shade the tank and give cover to fry and surface-dwelling fish. They help suppress algae by competing for light and nutrients.

Duckweed multiplies very fast, so scoop some out with a net every week and leave open areas. Floating plants can be kept inside a floating ring or behind a tubing barrier so they do not cover the whole surface.

A dense mat of floating plants blocks light, so light-loving plants below may become leggy or stop growing. Shade-tolerant anubias or cryptocorynes do not mind, but it is worth thinning the mat regularly.

Floating plants often turn brown when water drips or condensation keeps landing on their leaves, when strong flow tosses them around, or when it is too hot under the lid from the light. A calm surface and an air gap under the lid usually help.

Carpeting plants such as Hemianthus, Glossostigma or hairgrass grow low and form a green carpet in the foreground. Most of them need strong lighting, a fine nutrient-rich substrate and CO2, so they are more demanding than other plants.

Some plants, such as dwarf sagittaria, certain hairgrass species or dwarf four-leaf clover, can carpet the bottom without CO2, only much more slowly. More demanding carpeting plants without CO2 often grow upward, thin out and get covered in algae.

Plant carpeting plants in small clumps a few centimetres apart, pressing them into moist substrate with tweezers. Many aquarists plant them in a barely wet tank kept covered with film for a few weeks until they root, and only then fill it with water.

The mosses most often grown in aquariums are Java, Christmas, weeping, flame and similar mosses, plus riccia. They suit wood, rocks and shrimp tanks, because they collect microorganisms that shrimp and fry feed on.

Moss usually turns brown when debris builds up in it, flow is too weak, the water is too warm, or algae settle on it. Rinse it in a container of tank water, trim off the brown parts and improve water movement.

Spread a thin layer of moss between two stainless steel or plastic mesh sheets and fix them to the back glass or the bottom. Within a few weeks the moss grows through the holes, and then it only needs regular trimming.

In vitro plants are grown in a lab in a sterile gel inside a sealed cup. They carry no snails, algae or pests, so they are safe for shrimp, but they start out small and need time to adjust to the aquarium.

Take the plant out of its cup, rinse all the gel off the roots thoroughly and split it into small portions. Plant with tweezers, and for the first weeks avoid very strong flow and large fertiliser doses while the plants adapt.

Potted plants are larger, often grown above water and set in rock wool, which must be removed before planting. In vitro plants are smaller but completely clean, with no snails or algae.

Remove the pot and carefully pick the rock wool out of the roots so no pieces remain. Overly long or damaged roots can be trimmed, then plant it in the substrate or tie it to a decoration.