Doomed to Dissolve – Plants to Avoid in Freshwater Aquariums

Once upon a time you set up your first aquarium. You can remember the excitement of getting it all together, arranging everything perfectly, and introducing your first fish and plants. Chances are you also remember the disappointment and frustration when something in the tank just didn’t thrive the way you wanted it to. In many cases, beginner aquarists struggle with keeping live plants looking as good as they did in the store, but the speedy decline of pet store plants may not be due to your black thumb. While most plants offered in the aquarium trade are true aquatic plants, other plants simply aren’t meant for fully aquatic environments, waning and falling apart in the aquarium within days or weeks. 

True aquatic plants are those that are entirely or almost entirely submerged in their native habitat. Some will never break above the water’s surface, but many can thrive in drier seasons by forcing their top foliage to emerge from the water and to adapt to life in the air. The shape and texture of the emerged foliage often changes becoming more rigid and waxy. This foliage remains until the waters rise and the new growth reverts back to cope with watery surroundings. Unfortunately, terrestrial and bog plants do not adapt to such changes well, and these plants perish, unable to “breathe” in the tank.

If some plants aren’t meant to grow in an aquatic environment, then why are they sold for aquarium use and displayed in store tanks?  The simple answer may be lack of information or care on the matter. Most of the plants that fit this category are either marsh plants or plants whose cuttings will root easily in water. In supplier greenhouses, these plants are typically propagated in water and/or raised in hydroponic conditions. The roots adapt to taking nutrients from the water directly, but the foliage doesn’t adapt to being submerged long-term. The emerged growth of the plant is either potted or bunched then shipped to stores where they are tossed into tanks and marked for sale. These plants are actually suited better for vivariums, terrariums and paludariums, but they’re often available next to true aquatic plants and lines may become blurred. Before you know it you’ve purchased a beautiful plant that is doomed to rot away in your tank.

The easiest way to avoid bringing a doomed-to-fail plant home is to learn to recognize some of the common terrestrial plants offered for aquariums. Then it’s just up to you to fight the temptation to buy, even if they plant looks happy and interesting.

Here is a partial list of plants frequently offered by aquarium shops that should be avoided as submerged decor:

Acorus sp.. – Also known as sweet flag, and often sold in the variegated form, this plant’s grass-like leaves may seem to hold up for a while, but the pointed tips will eventually brown and the plant will not establish a root system. They’re related to the colorful irises used in ornamental ponds and landscaping and are better suited to such an application.
Alternanthera ficoidea – Also known as hedge or Joseph’s coat , this plant is offered in several different varieties for aquariums. This plant is sold as cuttings, and will often show promise by sprouting roots from the stems, but the foliage declines quickly and can create a big mess if left in the tank for too long.
Chlorophytum sp. – better known as the reliable “spider plant” or “airplane plant” these variegated plants are the same as the popular houseplants that hang in sunny windows everywhere. While the swollen roots take easily to moist soil or straight-up water, the foliage is not suited for the aquatic environment. 
Cyperus helferi – Related to popular marsh plants like papyrus and umbrella palm, this speciess can acclimate to grow in a fully submersed environment, but the adaptation time is lengthy. This plant may be best left to experienced growers who have the conditions and patience for them.
Marsilea sp. – “Water Clovers” can be very tempting to the novice. Keep in mind that several species are offered by the name, each with a different growth habit, and not all suited for totally submerged use. These plants are usually grown by suppliers emerged and the foliage on newly purchased plants will likely rot before the new submerged growth appears.
Ophipogon japonica – Usually labeled as Mondo Grass, this plant is doomed in a watery grave. Don’t even consider it.
Spathiphyllium sp. – Oh the lovely peace lilies also known as brazilian swords…these beauties can be quite a conversation piece in the right display, but not in an aquarium. These plants are easily grown hydroponically with robust, clean, white roots and are perfectly suited for betta vases and other applications where the foliage remains above the water’s surface. Blossoms and leaves don’t last too long under water.
Dracaena sp. – These variable plants come in several shapes, colors and varieties. You may have seen “lucky bamboo” offered at any variety of shops (not actually bamboo if you didn’t already know), but the most common offerings are “ribbon plants” (D. sanderiana) and “pineapple plant” (D. deremensis), and none of them belong in a fish tank. 
Hemigraphis sp. –  Too many people fall under the spell of the pretty purple plants in this genus. “Purple waffle” and “Dragon Flame” are equally unsuitable for aquatic use…seriously, save yourself the money, time and aggrivation these plants have to offer in exchange for the 2 days they’ll look pretty in the tank.

Pilea cadierei – You’d think something called an aluminum plant would be tougher. Not this guy! The soft, yet appealing, silver-spotted foliage doesn’t stand a chance in a tank.
Syngonium sp. – often called Arrowheads, but not to be confused with the marsh-loving Sagittarias of the same name. Best left for humid terrariums.
Trichomanes javanicum – It may look like a true aqautic, it may feel like a true aquatic, but in the end this nifty little fern is meant for a humid, not aquatic, environment.

Just because these plants won’t thrive under the water, doesn’t necessarily mean they can’t be used in aquariums. Next time I’ll write about some ways you can utilize some of these notorious not-for-aquarium plants.

Until then,

Patty

Peace Lily image referenced from wikipedia and originally posted by UshaJ
Spider plant image referenced from wikipedia and originally posted by Wildfeuer
Pilea cadierei image referenced from wikipedia and originally posted by Fanghong