Beginner's guide to avoiding nonaquatic plants at shops

The tank above looks good to the eye but contains a few non-aquatic plant species.

Introduction

Planted aquariums are becoming increasingly popular, and aquarium shops can stock a bewildering array of plant species. The biggest pitfall for beginners is that aquarium shops often stock non-aquatic plant species that do not grow well in the aquarium long term. This is due to a mixture of lack of knowledge and supply issues. Among the aquatic plants that can be used in the aquarium, a large number of species can grow emersed out of water, and the same plant species look very different when grown emersed. Beginners can find it difficult to identify plants because a species can look so different depending on how it is grown.

This guide highlights some common non-aquatic species that hobbyists should avoid, and also shows the different forms that aquatic species can take when grown above water.

Nonaquatic vs Aquatic plants

If your plant does not survive in your aquarium, one reason might be that it is nonaquatic in the first place.

• A non-aquatic plant is one that cannot grow well in water for long periods of time. This includes many marsh plants, which can grow well with their roots in the water for a long time, but require their leaves to be in the air. These plants are not adapted to fully submerged conditions.

• An aquatic plant is one that can grow well in the long term while submerged in water. These are species that can be fully adapted to grow underwater. Many of these species include marsh plants that can grow just as well out of water, which can be confusing for new hobbyists.

• A true aquatic plant is a term we use for plants that grow only under water in the wild. They make good aquarium plants because they are naturally adapted to grow underwater.

The majority of plants used in aquariums fall into the second category above. These are marsh plants that can grow well both above and below the waterline. True aquatics do exist, but they are not as common as amphibious marsh plants.

However, many aquarium shops import non-aquatic marsh plants. These plants may have wet roots but cannot be submerged for long periods. This happens because the knowledge of plants in aquarium shops, outside of shops specialising in planted tanks and aquascaping, tends to be poor. Many aquatic retailers import plants from nurseries that cater to landscapers who mainly service ponds and bog gardens; in their use of marsh plants, they tend to use them for emergent growth above water, with wet roots, rather than as submerged plants.

Nonaquatic species to avoid

Many aquarium shops place non-aquatic species in aquarium displays or sell them submerged in water packs. This is done to fool the customer and is no indication that the species will actually grow well submerged in the long term. Non-submerged marsh plants can often last for many weeks (months) in the aquarium before eventually deteriorating. Their slow decay attracts algae. Often these plants will elongate in an attempt to break through the surface of the water, but will not gain any real mass. These plants are tolerant of short-term flooding in the wild, but do not have the adaptations necessary for long-term submerged growth.

Alternanthera bettzickiana

There are many aquatic Alternanthera species. However, Alternanthera bettzickiana cannot grow well submerged long term. It has attractive hooked shaped leaves. In aquariums, the plant can last a few weeks but will weaken and rot eventually. 

Alternanthera 'broadleaf'

This Alternanthera species looks attractive due to its reddish foilage. However, it cannot survive underwater long term. Often sold tied to wood. Looks similar to other aquatic species such as Ludwigia repens.

 Alternanthera sessilis

Alternanthera sessilis has very attractive deep purple leaves. Countless hobbyists have been lured into buying this plant in hope of growing it in their aquarium. It does not fully adapt to underwater growth and will deteriorate in a couple of weeks.

The picture below shows Alternanthera sessilis (left) beside Ludwigia glandulosa (right). Ludwigia glandulosa is an actual aquatic plant that can grow well long term in the aquarium. A. sessilis can be differentiated by its more rounded leaf tip compared to L. glandulosa. Ludwigia glandulosa has an alternate leaf arrangement, while A. sessilis has an opposite leaf arrangement. 

Alternanthera ficoidea

Alternanthera ficoidea is another nonaquatic Alternanthera species. It looks very similar to Staurogyne repens, an aquatic plant. It has distinctively hooked shaped leaves, which is the easy way to identify it. It also comes in reddish varietals (picture below).

Hemigraphis repanda

Hemigraphis repanda (left) , also known as 'dragon's tongue', is another common nonaquatic. It has attractively shaped leaves with a purple underside. It looks very similar to the aquatic plant Hygrophila pinnatifida (right). It has shallower narrow lobs and is generally much thinner than Hygrophila pinnatifida.

Hemigraphis colorata

This plant has attractive purplish leaves but cannot grow well long term underwater. Attracts algae as it deteriorates slowly while submerged.

Ophiopogon japonica

This dark green plant looks like it will make for a good bush in the aquarium. However, it is not aquatic. Small bunches are often sold as aquarium plants, but adult plants are actually much bigger sized like above. Identified by its dark green foliage with visible veins. A similar looking aquatic plant is Eriocaulon vietnam.

Cyperus haspans

The flower stalk of Cyperus haspans is often sold tied onto wood. It looks like an Eriocaulon but is actually a nonaquatic plant. This portion is merely the flower head - the full size Cyperus plant is a couple of feet tall.

A mix of non aquatic species in a single picture:

Dracenia species, Cordyline red & other Cordyline species, Selaginella species

Selaginella willdenowii grows well in moist soils, however, it cannot be grown submerged long term.

Dracenia species are common houseplants, but they do not belong in an aquarium.

Many of the above species look attractive and are cheap, but none of them will last long under water. Deteriorating plants will pollute the water rather than clean it, contributing to algae and organic waste. Many vendors will display these plants submerged in their tanks, but this is no indication that the species are adapted to submerged growth. Healthy specimens of the above plants can last for a few months, which only confuses the hobbyist more, as when they start to die, the hobbyist is left wondering if it is due to their tank conditions, as the plant has 'survived' for some time.

Aquatic plants: Emersed vs submerged growth

Many aquatic plants can also grow above water. However, these plants take on a different growth form when grown above water, which we call emergent growth forms. Farms prefer to grow aquatic plants above the waterline where possible, as they grow faster and are easier to manage and ship in their emergent form.

Aquatic plants have very variable growth forms

Aquatic plants change the shape and size of their leaves and stems as part of their adaptation to moisture levels and whether they are under water. This results in a huge variety of potential growth forms for a single species. Depending on whether the plant has been grown in a dry, wet or submerged environment, the leaf shape and colour of the plant can vary. Many red aquatic plants look green in their submerged form. The colour only develops after the plant has been grown underwater for some time. Emersed forms also tend to have thicker, stiffer stems and leaves.

To make matters worse for hobbyists, different aquatic plants can have submerged forms that look similar. Without flowers or a submerged sample, it can be difficult to accurately identify aquatic plants. The best way around this is to only buy plants from shops that specialise in planted tanks and aquascaping. The plants listed below are all aquatic plants that can be grown in an aquarium - however, they are often grown submerged by farms and sold in their submerged form in shops.

Alternanthera reineckii 'rosaefolia'

Alternanthera reineckii 'rosaefolia' has reddish leaves when grown submerged (right). It has mostly green leaves when grown emersed (left).

Hygrophila polysperma 'sunset'

This variegated version of Hygrophila polysperma has attractive pink leaves when grown submerged(right). The emersed growth is mostly green.

Hygrophila difformis (Water wisteria)

Water wisteria has broader green leaves when grown emersed (left). Its submerged form has more divided leaves (right).

Ludwigia 'super red'

Ludwigia Super red can be green or red when grown emersed. Under less light the leaves are more greenish when grown emersed (left). The leaves grow very easily red submerged though(right). 

Ludwigia repens

Ludwigia repens has reddish/orange tones when grown submerged (right). The emersed grown plants are largely green in color (left). 

Ludwigia arcuata

Ludwigia arcuata has very thin orange/reddish leaves when grown submerged (right). The emersed form has much broader leaves that are mostly green (left).

Ludwigia pantanal

Ludwigia inclinata var. verticillata 'Pantanal' has fine reddish leaves when grown submerged (right). When grown emersed, the plant has thicker, broader green leaves (left). 

Rotala rotundifolia and its variants (Rotala H'ra, Rotala Colorata, Rotala green)

Rotala H'ra has round leaves in its emersed form (left) and thinner leaves that are yellowish or red in its submerged form (right).

Rotala rotundifolia Green has round green leaves in its emersed form (left) and thinner green leaves and stems in its submerged form (right).

Rotala rotundifolia 'colorata' is another variant of Rotala rotundifolia that gets colorful more easily. However, the emersed form (left) has round green leaves that is difficult to differentiate from emersed forms of Rotala H'ra and other Rotundifolia species.

General tips on buying aquarium plants

• Many aquarium shops put both aquatic and non-aquatic species in tanks when they sell them. If you see the plant submerged in water in the shop, there is no guarantee that the species is aquatic.

• Non aquatic plants can last quite long in some aquariums, up to a few months, but they will not adapt in the long term. Deterioration is therefore certain, but can take a long time to manifest itself.

• Submerged plants have water to support their structure - these plants often become limp when taken out of the water. Emersed plants tend to be stiffer and can stand up straight when taken out of the water. This may indicate whether the plant is submerged or not.

• Many shops import plants in their submerged form. As long as the plants are healthy, they should adapt quickly to submerged conditions. There is little need to buy only submerged plants. Ultimately, the healthier specimen will have a better chance of adapting to the aquarium.

• Buying aquarium plants is a bit like buying fresh lettuce. Look out for yellowing or wilting leaves, which can indicate that the batch of plants is not as fresh as it could be. Plump, firm and brightly coloured leaves are a good sign. Soft stems, yellowing leaves with brown spots or mushy growth are a bad sign. Fresh, well-grown plants have more energy reserves and will therefore adapt better when added to a new tank environment.

• Check out this guide on how to choose tissue culture plants