Aquatic Plant Primer
Why live plants? Live plants are among the most beautiful and natural aquarium decorations available. They also are natural filters, adding some oxygen and removing fish waste from the aquarium. Those are ample reasons for many aquarists to consider them, but live plants have a charm of their own as well; caring for them and observing their growth, development and reproduction can be just as fascinating and rewarding as fishkeeping. In fact, there are numerous aquarists who keep fish primarily to provide carbon dioxide and fertilizer for their plants!
Here are some practical suggestions for success with aquarium plants:
Choose the right plants. Aquatic plants do not all have the same requirements for survival. Certain lighting, temperature, hardness and pH conditions will allow some plants to survive and thrive while others perish. If you are unwilling to match your aquarium conditions to those required by a demanding species, stick to the varieties that will do well under your conditions. Plants that usually do especially well in Milwaukee water and standard lighting and temperatures include Amazon Swordplants, most Vallisnerias, some Cryptocorynes, Banana Plants, Apongetons, Hygrophila, Water Wisteria, Anacharis (Elodea) and Hornwort.
Plant them carefully. Aquatic plants are much more fragile than their terrestrial cousins. Rough handling can cause damage to leaves, stems and roots. Plant them in two to four inches of fine or medium aquarium gravel. Well-rooted plants like Swords and Vallisnerias should be planted so their "crowns" (where the roots end and the leaves begin) are visible just above the surface of the gravel. Stemmed plants like Anacharis and Hygrophila should simply have an inch or two of stem pushed gently into the gravel. Any rubber bands, lead weights or plastic pots are meant to be temporary and are best removed if the plants have enough roots to hold themselves in place.
Give them enough light. The above-mentioned hardy plants should survive under 10 to 12 hours of light per day from the standard fluorescent light that came with your tank (less than 1 watt/gallon). Many other species may require two, three or more full-length fluorescent bulbs for normal growth. (And no, you can't just leave the light on longer; the plants need the brightness rather than the hours.) Special plant bulbs are a good investment, especially if you can't get as many bulbs on the tank as you'd like. Change the bulbs frequently (every 8 to 12 months) for best results, as fluorescent lights lose much of their intensity and spectrum with age. Finally, keep the light's reflector and the tank's cover clean, so as much light as possible finds its way into the aquarium.
"Feed" them. As plants grow, they absorb many chemical nutrients from the water and gravel bed. Some of these chemicals, for instance nitrogen and phosphorus are usually abundant in fish waste and need not be added separately. Others, especially iron and potassium, need to be added regularly in tanks with lots of well-growing plants. If you're setting up a new aquarium especially for plants, adding laterite clay to the lower layer of gravel is highly recommended as a slow release iron source. In addition, liquid and/or pellet plant nutrients should be added routinely. In thickly planted, well lit aquaria, adding a carbon dioxide generator (either a commercial or do-it-yourself model) is worth considering.
Beware of toxic chemicals. Even many of our common chlorine neutralizers, water conditioners and aquarium salts have adverse effects on some plants, especially if they are dumped in concentrated form right on the plant leaves. More dangerous are many of the fish medications. "Ich" cures containing malachite green and some of the antibiotics seem safe enough, but others can turn plants to mush almost overnight. It's best to move sick fish to another aquarium for treatment rather than treat a planted tank.
Avoid vegetarian fish. Some fish, notably silver dollars, Buenos Aires tetras, severums and tinfoil barbs will devour most plants to the roots in no time at all. Others, like most larger cichlids, will keep plants uprooted and mangled. Bristlenose plecostomus leave most fine leafed plants alone, but demolish the wide leaves of sword plants in particular. Many common community fish, such as mollies, swordtails and tiger barbs may also browse occasionally on plants, but seem to do little damage. Supplementing their diet with a good vegetable food will help satisfy their needs.
Change water often. Plants, like many fish, prefer frequent (once per week) but smaller (20% or less) water changes. As with any water change, make certain the new water is dechlorinated and of a similar temperature to the aquarium.
Watch out for algae. Some algae growth is normal in any aquarium, especially one with extra lighting. This natural amount can be kept in check with the addition of a few algae-eating fish like otocinclus, Siamese algae eaters, stone lappers or certain plecostomus. Rapid algae growth, however, is a warning that something is amiss. Overfeeding of fish is the most common cause of algae blooms, followed by inadequate water changing, too much yellow light, and poor quality plant fertilizers.
Watch out for snails, too. While snails pose little threat to aquatic plants, they can multiply to the thousands in a few months and affect the overall appearance of the tank. Many snails and eggs come into the tank on the plants themselves, and the best defense against them is to inspect all new purchases thoroughly before adding to the tank. A clown loach or two in the aquarium will help polish off any snails you missed, but they key is to address the problem before it gets out of hand.
Read about them. This brief article is by no means all there is to know about the care and maintainence of aquatic plants. Invest in a couple of good plant books, or at least look up the names of any plants you are considering adding.
For a list of aquarium plants we usually stock, see Aquarium Plants.
Copyright © 1996 James M. Kostich
All rights reserved.