How to Decorate a Fish Tank: Easy Steps and What to Check First

Fit the background on the outside first

Aqueon: “Background material should be installed on the outside of the aquarium before placing the aquarium on the stand and filling it with water.” Practical Fishkeeping, a fishkeeping magazine: “Dark backgrounds help ‘set off’ the plants, décor and fish”. Our guide to painting the back of an aquarium compares paint, vinyl and 3D options.

Lay a plate for heavy rocks, then the substrate

Tropica: “In places where big rocks are to be placed later, a thin styrene plate can be placed before the substrate and gravel in order to protect the glass bottom.” Swell UK, an aquarium retailer: “When buying gravel check that it says that it is inert, meaning that it won’t raise the pH, and avoid rocks aimed at saltwater tanks like Ocean rock and Tufa rock, which are beige in colour.” Pisces USA, which sells Galaxy Sand, says in its FAQ: “Being an inert substrate, Galaxy Aquarium Sand does not alter the pH or hardness of the water”. Seachem, an aquarium products maker, on its Onyx Sand: “Onyx Sand™ is not chemically coated or treated, and as a carbonate rich sand, it has a slight buffering capacity that may raise pH by 0.1 – 0.5 pH units (depending on source water characteristics).” It adds: “Although it is pre-washed, because Onyx Sand™ is a natural product, it may become dusty in transit and require rinsing before use to remove any residual dust.” Rinse gravel as Aqueon says (What you need). ADA, a planted-aquarium maker, says the opposite for its Aqua Soil Amazonia: “Rinsing in water before use is NOT necessary, as it makes granules to crumble, and water cloudy.” Follow your substrate’s label. For soil under gravel, see layering substrate in a planted tank.

Place rocks, and check what they do to the water

Buce Plant, a plant retailer: “Two rocks that are known to raise water hardness are Seiryu Stone and Pagoda Stone.” For soft-water fish, Maidenhead Aquatics, a UK retailer chain: “Avoid using decor in your tank which leaches minerals and makes the water hard and more alkaline e.g. limestone, barnacles etc.” For goldfish (it names fancy varieties), Aqueon: “Avoid decorations with sharp edges and abrasive rocks such as lava and tufa, which may tear delicate fins as well as eye sacs on bubble eyes, celestial eyes, moors and telescopes.” Aquasabi, an aquascaping retailer, says: “It is very advisable to clean resp. rinse all stone decoration under running water before use in an aquarium.” Its notes on calcareous stone under CO2 are in our aquascaping guide. If your water drifts, see how to lower pH, raise pH or soften aquarium water.

Prepare the driftwood: soak it, or accept the tint

Galapagos, which sells the wood above: “We recommend presoaking natural woods in a separate tub of water and changing the water daily. This can be done for up to two weeks and will help remove excess tannins, a non-toxic organic substance, that can dye your tank water a tea color. Use a clean brush to remove any extra debris and consider boiling the wood for one hour to sterilize before adding to your aquarium.” Boiling water scalds, so handle the pot with care (our caution). Soak times differ: Aquasabi, an aquascaping retailer, says “At least 1-2 weeks with a water change daily if possible.”; Aquael, an aquarium equipment maker, says “it should be soaked in water for several weeks”. Aquasabi: “The tannins also acidify the water slightly, which can lower the pH. This effect can be positive for sensitive fish species but undesirable for others.” ADA’s guide disagrees on soaking: “Getting Tannins Out of Driftwood Is Not Required”.

Add ornaments, and feel every edge

Bettaboxx, for bettas: “Some decorations can have sharp edges or protruding features that a betta could easily tear its fins or snag itself on.” An owner on a Fishlore forum thread: “You can run a nylon stocking over it and if it snags a nylon there’s a chance it could snag a betta fin.” Swell UK, on high pH: “If you have any ornaments that look like they are made from concrete or any rocks that aren’t inert like slate, remove them, do several large water changes and it should make a difference.”

Put tall pieces at the back, with water flowing round the heater

Aqueon: “Place taller plants and décor items near the back of the aquarium to provide backdrop and hide filter tubes, heaters and cords, with progressively shorter decorations towards the front.” Fluval’s E heater manual: “Place the heater where the unit is unobstructed, and where there is a free flow of water to ensure even heat dispersion.” and “Be sure there are no rocks, decorations or gravel obstructions touching the heater to create uneven heat.” Aquasabi says that on a golden-ratio grid of four lines and nine areas, eye-catchers “can be placed” where two lines intersect, and that focal points “are often placed at intersecting lines when the rule of thirds or the golden ratio are used.”

Add plants, live or artificial

Aqueon installs artificial plants with the rockwork, but says: “Live plants and fish, should not be added until the aquarium has been running for at least 48 hours.” Tropica plants in shallow water during setup instead (our aquascaping guide has its steps). See our beginner plant list and planted aquarium light roundup. Then fill, and start the equipment as in steps 3-5 of the next section.

Unplug every appliance before your hands go in

Fluval’s AquaClear filter manual (Fluval makes filters and heaters): “Always unplug or disconnect all appliances in the aquarium from electricity supply before placing hands in water, before putting on or taking off parts and while the equipment is being installed, maintained or handled.” and “Never yank cord to pull plug from outlet. Grasp the plug and pull to disconnect.” Dr. Jessie Sanders, an aquatic veterinarian: “Unplug filter and lights.” and “If you have any UV lights, unplug those too.” If you have a sump, she also says: “Close any valves if you have a sump so it doesn’t overflow.” Fluval’s E heater manual: “If it has to be taken out of the water or when transferring or changing the water, disconnect the heater from the power source and wait for at least 30 minutes to allow it to cool down.” It also says: “To avoid injury, do not touch hot parts.” Keep your hands off the heater until it has cooled (our reading). Wash your hands and put on gloves (CDC, above, which also says who should not do this job).

Move, add or remove pieces

Everything stays unplugged until step 4. Prepare new pieces as in steps 2-5 above, and keep them off the heater (step 6).

Refill, then prime the filter

If you took water out, refill as in our water change guide. Fluval: “Do not allow filter pump to run dry.” Dr. Sanders: “Prime your filtration by pouring some tank water into the filter base.” She adds: “Canister filters may have a priming operation or need water forced down the intake.” and “If you are unsure if your filter should or needs to be primed, contact the manufacturer.” If you have a sump: “Open any valves you previously closed on your sump and other filtration.”

Plug in with a drip loop, hands out

Aqueon: “Prime the filter and plug it in using a drip loop. A drip loop is when you allow the cord to drop below the outlet before it rises up to plug in.”

Bring the heater back

Hydor, a heater maker: “Hydor Heaters MUST NOT be used out of water. When undertaking water changes Hydor recommend that the heater is turned off and unplugged from the power socket at least 30 minutes before any waterchange. The Heater can ONLY then be turned back on when the Aquarium is full and the heater is completely submerged.” Makers’ waits differ, and they are given for installing a heater. Fluval’s E heater manual, for installing the heater in the aquarium: “Allow heater to acclimatize in the aquarium water temperature for 20 minutes before plugging it into the electrical outlet.” Aqueon, for a new setup: “After 10 minutes, plug the heater in.” Neither source says how long to wait when a heater stayed in the water; your heater’s own manual has the final word. Wash your hands again when you finish (CDC, above).