FAQ: Tank Decor for fish

Keep the decoration for a few weeks in a bucket of water with known parameters and use tests to compare hardness and pH with a control sample. You can also track the tank’s parameters for a few weeks after adding the new piece.

Yes, nitrifying bacteria that break down ammonia and nitrite settle on every surface, especially porous rock, wood and substrate. That is why you should not clean all the decor at once or wash it with chlorinated water or detergents.

Algae need light, so less grows in shade under roots or behind rocks than in bright spots close to the light. Decor in bright areas needs cleaning more often, and shady spots suit slow-growing plants and mosses.

Algae on rocks are common in a new tank until the balance settles. A shorter light period, dense planting, regular water changes, moderate feeding and algae eaters such as snails or shrimp all help.

Yes, using safe materials: inert rocks, hardwood, unglazed clay, aquarium-safe silicone or epoxy resin rated for water contact. Avoid paint, varnish, metal and plastics of unknown composition.

Some epoxy resins described as safe for food or water contact are used in aquariums to coat backgrounds and decor. The key is to let the resin cure fully, as the manufacturer directs, before submerging the piece.

Glue clean, dry flat rocks into a cave shape with aquarium-safe silicone and let it cure for at least a day or longer, as the maker directs. Rinse the hide and check it is solid before putting it in the tank.

Yes, if the leaves were gathered dry after falling in autumn, away from roads and sprayed fields. Rinse and scald them so they sink, and in the aquarium they will release tannins and become food for shrimp.

Collect rocks and branches in clean places away from roads, factories and fields, and only where it is allowed. At home scrub them, test the rocks with vinegar, dry and scald the branches, and leave out any find you are unsure of.

Wood washed up by the sea is soaked with salt and may carry pollutants, so it needs long soaking in fresh water with frequent changes. Wood prepared for aquariums is safer, especially if you keep sensitive fish or shrimp.

Expanded clay pellets are inert and porous, so they are sometimes used as a lower substrate layer or filter media. They are light and can float up, so they must be capped with other substrate and rinsed well before use.

Make a sand river by laying a strip of light sand between rocks or plants that winds from the front into the depth of the tank. Edge it with small stones so the sand does not mix with the substrate, and keep it clean with a siphon.

An undergravel filter needs coarser gravel that water flows through freely, and sand clogs it. If you use such a filter, choose gravel of about 3–5 mm and siphon it regularly.

Fish that dig or burrow, such as spiny eels, kuhli loaches or some cichlids, need a deep layer of soft sand with no sharp particles. In such a tank set the rocks on the bottom glass so the fish cannot undermine them.

Do not pull the fish out by force: carefully lift the decoration with the fish into a container of tank water and let it swim out by itself, or gently help it. Afterwards replace the decoration or enlarge the openings, watch an injured fish and contact a vet if needed.

Some fish, especially goldfish and large cichlids, take substrate into their mouths while foraging and can occasionally swallow or choke on small gravel. Choose very fine sand they spit out, or large pebbles that do not fit in their mouths.

Take rocks and wood out and pack them separately so their weight does not press on the tank glass. To preserve beneficial bacteria, some decor and the filter media can travel damp in tank water, and the substrate in sealed buckets.

It is not advisable, because heavy substrate and rocks can crack the glass or damage the seams in transit. Before moving a tank, remove the water, decorations and substrate, and carry it empty.

Clean and dry decorations completely before storing them so they do not go mouldy, wood especially. Rinse them before reusing, and soak wood again, as once dry it may float again.

Before a big rescape, move the fish to a separate container or tank with the old water and a running filter. Change substrate and decor carefully, and for a few days afterwards monitor water parameters, as ammonia may rise.