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 number of plant species. The biggest pitfall for beginners is that aquarium shops often stock nonaquatic plant species that do not grow well in the aquarium long term. This is due to a mix of poor knowledge and supply side issues. Amongst aquatic plant species that can be used in the aquarium, a large number of species can also grow emersed outside of water, and the same plant species look very different when grown emersed. Beginners have difficulty identifying plants due to how different a species can look depending on how it is grown.

This guide highlights some common nonaquatic species that hobbyists should avoid, and also shows the different forms that aquatic species can be 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 nonaquatic plant is one that cannot grow well long term submerged in water. This includes many marsh plants that can grow well long term with their roots in water, but require their leaves to be in air. These plants do not adapt to fully submerged conditions.

• An aquatic plant is one that can grow well long term while submerged in water. These are the species that can be adapted fully for growing submerged. Many of such species include marsh plants that can grow equally well out of water, which makes it confusing for new hobbyists.

• A True aquatic plant is a term we give for plants that only grow underwater in the wild. They make good aquarium plants as they are naturally adapted to underwater growth.

The majority of plants that are used in the aquarium fall into the second category above. They are marsh plants that can grow well both above the water line and below the water line. True aquatics, while they exist, are not as common as amphibious marsh plants. 

However, many aquarium shops import nonaquatic marsh plants. These plants can have wet roots but cannot be submerged long term. This happens because plant knowledge among aquarium shops tends to be poor outside of shops that specialize in planted tanks and aquascaping. Many aquarium shops import plants from plant nurseries that cater to landscaping companies that mainly service ponds and bog gardens; in their usage 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 put nonaquatic species in aquarium displays or sell them submerged in packets of water. This is only done to fool the customer, and is no indication that the species can actually grow well submerged long term. Nonaquatic marsh plants can often last many weeks (months) in the aquarium, then eventually deteriorate. Their slow deterioration attracts algae. Often these plants elongate in length to try to breach the water surface, but do not have any real gain in mass. These plants are tolerant of short term flooding in the wild, but do not have the adaptations required to grow underwater long term.

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 species above look attractive and come at cheap prices, but none of them will last long term underwater. Deteriorating plants pollute the water rather than cleanse it, and contribute to algae and organic waste. Many sellors will have these plants submerged in their tanks on display, but that is no indication that the species are adapted to submerged growth. Healthy samples of the plants above can last a couple of months, which only confuses hobbyists more, as by the time they start to die, the hobbyist is left wondering whether it is due to their tank conditions since the plant 'survived' for some time.

Aquatic plants: Emersed vs submerged growth

Many aquatic species can also grow above water. However, these plants take on a different growth form when grown above water, we call this emersed grown forms. Farms prefer to grow aquatic plants above the water line if possible as they grow faster and are easier to manage and ship in their emerse grown forms.

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 underwater. This gives rise to a huge variety of potential growth forms for a single species. Depending on whether the plant was grown in a dry, moist or underwater environment - the leaf shape and color of the plant can vary. Many red aquatic plants look green in their emersed forms. The color only emerges after the plant has been grown underwater for some time. Emersed forms also tend to have thicker, more rigid stems and leaves.

Making things even more difficult for hobbyists, different aquatic plants can have emersed forms that look similar. Without flowers or a submerged sample, having accurate IDs for aquatic plants can be difficult. The best way to get around this is to only purchase plants from shops that specialize in planted tanks and aquascaping. The plants below are all aquatic plants that can be grown in the aquarium - however, they are often grown emersed by farms and are sold in their emersed forms at 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 nonaquatic species into tanks when selling them. Seeing the plant submerged in water at the shop is no guarantee that the species is aquatic.

• Nonaquatic plants can last quite long in some aquariums; up to a few months, but they will not get adapted in the long term. So deterioration is certain but can take a long time to manifest.

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

• Many shops import plants in their emersed forms. As long as the plants are healthy, they should adapt quickly to submerged conditions. There is little need to buy only submerged grown plants. Ultimately the heathier specimen will have better chances at adapting to the tank.

• Buying aquarium plants is similar to buying fresh salad. Look for yellowing or decaying leaves that can hint that the batch of plants is not as fresh as it could be. Plump, stiff and vibrant colored 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 stores and this enables them to adapt better when adding to the new tank environment.

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