Ferns in the aquarium
By growing aquatic plants in your indoor aquarium, you are able to create a beautiful natural display and also provide healthier conditions for your fish to thrive. As the plants grow they will absorbed nutrients that will make algae less likely to be problem and the plants will produce oxygen and improve the water quality. Many aquarium plants are in species of ferns that will happily adapt to aquatic life.
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Water
Most aquatic plants are happiest with soft, slightly acidic water. Rainwater can be used, but if you are also keeping fish there might be a risk of introducing disease, parasites and polluting chemicals into the aquarium. However, this is less of an issue if you are just maintaining an aquarium to keep ferns!
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Algae
Algae can be a problem if the aquarium has not found a balance or the conditions are inconsistent. Algae will grow vigorously in harder water, so using soft acidic water is helpful. Too much light can also cause algal problems. 8–10 hours a day is sufficient. There can also be a siesta in the middle of the day for 2–4 hours.
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Lighting
Additional artificial lighting is required for most aquariums. Overtime tungsten, fluorescent and mercury vapour bulbs have been replaced with LED equivalents. Many people have had success using basic LED floodlights for plant growth in the aquarium. Use a timer to establish a consistent rhythm.
Choice Ferns
This group of ferns includes the aquarium plant stalwart, Java Fern. Many are technically aquatic epiphytes and lithophytes, meaning they grow submerged but attached to wood or stone. There are also floating ferns like Salvinia that can be an interesting addition to the aquarium. Most of these are readily available from aquarium suppliers and online.
Java Fern
Leptochilus pteropus
This is readily available in the aquarium trade usually as Microsorum pteropus. There are various fancy cultivars. It's rhizome needs to be attached to wood or rocks. They are quite adaptable but can suffer if there is a lack of nutrients.
Asian Water Fern
Bolbitis heteroclita
A small fern that can adapt well to submerged life in the aquarium. It's prone to algae due to its slow growth. There are several cultivars and clones available. These also adapt well to growing in terrariums and warm humid glasshouses.
African Water Fern
Bolbitis heudolotti
A very attractive dark green fern that gently moves in the water current. Its rhizome attaches to wood.
Indian Fern
Ceratopteris thalictroides
A quick growing aquatic fern. It is very adaptable and can grow as a floating plant, a fully submerged plant or emergent plant in shallow water. It responds well to CO2 supplementation and fertiliser.
Water Spangles
Salvinia auriculatum
A quick growing floating fern. It likes fertile water and needs to be regularly thinned out as it can prevent light from penetrating the aquarium. Excellent for reducing light and absorbing excess nutrients.
Water Clover
Marsilea minuta
A pretty fern that when submerged slowly creates a carpet covering the substrate of the aquarium. In shallow water or damp substrate it takes on it's more familiar four-leafed clover appearance. Can take some time to establish.
Caring for your ferns in your aquarium.
Most aquatic plants are happiest with soft, slightly acidic water. A major factor is that the plants will have more available CO2 in these conditions. Investing in a CO2 injection system will make a noticeable benefit to aquarium plants. There are also ‘liquid carbon’ additives available now that claim to make carbon more available to plants, if CO2 injection is not possible. The theory is that when the molecule breaks down it releases carbon dioxide into the water. The science is flaky, and the amount of carbon released seems unlikely to make much difference.
Most tap water is not soft. In an ideal world you may want to consider a water softening system, either a two-column water deionizer or a reverse osmosis system. Standard domestic ion exchange water softeners are not suitable due to excess sodium chloride. Pure water will need to be ‘remineralised’ before being used in an aquarium. All this water preparation is very time consuming and needs an advanced level of commitment. Some aquarium shops will sell deionised water specifically prepared for their customers. Rainwater can be used, but if you are also keeping fish there is a small a risk of introducing disease, parasites and polluting chemicals. However, this is less of an issue if you are just maintaining an aquarium to keep ferns.
The water temperature needs to be maintained around 25 °C using an aquarium heater. Lower temperatures can work for many aquatic ferns although growth will be slower. A water filter is recommended, although not essential, to help circulate the water. Pumping air into an aquarium is not recommended, although it is a good way to circulate the water, it will drive out carbon dioxide which is required for good plant growth. Undergravel filters will interfere with root growth, so should not be used if you intend to grow plants. Small regular water changes are also recommended to reduce the general build-up of salts, like nitrates, over time. For the serious aquarist, test kits are available to monitor many factors of your water chemistry.
There are many substrates on the market, available in many colours. Modern aquarium gravels designed for plant growth tend to be finer, approaching the consistency of sand. Normally they are made from inert materials, either natural rocks, usually silica sands, or man made products. If you are growing aquatic epiphytes and lithophytes you only need a very shallow depth of substrate and this is primarily for aesthetics. Newer ‘aquasoils’ are available which resemble fine gravel but are actually small balls of mineral rich volcanic ash soil that is then baked. Their composition will help to slightly lower and stabilise the pH of the water which is beneficial to most aquatic plants.
Aquarium plants will need fertilising. General aquarium plant fertilisers differ from regular NPK fertilisers and should contain a balance of nutrients for the needs of your plants. Over-fertilising will encourage algae growth.
Collections
Developing and maintaing a fern collection. How to safeguard your collection for the future.