My small desktop aquarium at my office has Amazon swords (Echinodorus bleheri) and windelov Java fern (Microsorum pteropus 'Windelov'). This aquarium has slightly less than 1 watt per gallon of lighting and no added CO2. It is a slow-growth tank, even though Amazons can be very fast-growing plants if given enough CO2, light and nutrients. This 6-gallon acrylic tank usually requires very low maintenance. I feed the few fish and add trace mix three times per week. Things seemed OK for about two years, but suddenly Java fern melt began to appear. Java fern melt is a rather suddenly appearing and protracted condition of deterioration of the leaves: The leaves develop spots and become mushy in places, then whole leaves rot. Yet one can remove the leaves, and the rhizome remains viable. The Amazons, however, continued to look fine.

I have had Java fern melt before, and each time, I was able to clear it up with one of two methods. In the more common case, I had inadvertently allowed the nutrient levels to get too low. Although Java fern is a slow-growing plant, it still needs a modicum of nutrients. Boosting the nutrients brings the Java fern back to life. But this raises the question of why the swords, which are typically fast-growing and nutrient-ravenous plants, would continue to appear healthy while the Java fern, which is a slow-growing plant, deteriorates. Other plant experts and I have seen this condition, and correcting for low nutrients revives the Java fern. It seems that the swords, being rooted plants, can obtain nutrients from the substrate if the substrate is mature and rich, even if there are few nutrients in the water column. The Java fern, being a plant that attaches to wood and rocks with a rhizome, cannot benefit from nutrients in the substrate. So, when the nutrients become too few in the water, the slower-growing plant shows deficiencies, because it is not rooted.

Another condition that will cause Java fern to melt is a proliferation of blue-green algae (BGA), which are bluish-green "algae" that grow like film (actually they are cyanobacteria, bacteria that photosynthesize like algae). It is easily lifted from the surface on which it grows, feels somewhat slimy and smells unpleasant. It tends to grow in aquaria with plant nutrient deficiencies.

If BGA gets a good foothold in an aquarium, it can begin to cover the Java fern leaves, preventing the Java fern from obtaining nutrients. BGA is easily eradicated by a three-day blackout. Turn off the lights, and cover the tank with a blanket for 72 hours - and  add erythromycin. This is available as an antibiotic for tropical fish, and used at half dose, usually knocks out BGA in about three days. Once you get rid of the BGA and fix the original nutrient deficiency that spurred its growth, the Java Fern can again flourish and the BGA will be kept at bay.

Q. I would like to know why my fern is turning "crispy." I've left it alone, and new plants are starting to form from the bottom. I don't want it to look like crispy. I turn the lights on for 12 hrs a day. Thank you for your time.
-- Santiago Silva
Willacy, Texas

A. I'm not sure what fern is in question or what "crispy" means in this context, but I suspect it is an early sign of Java fern melt.

Another condition that seems to cause some plants to get "crispy" looking is a lack of calcium, magnesium or both. Usually, both are present in tap water--but not always enough. One can supplement both of these trace minerals with some calcium carbonate (the stuff seashells are made of) and magnesium sulfate (Epson salts). A pinch of each at a water change is plenty in a 10-gallon aquarium.

Q. My question concerns the water sprites I have in a 55 gallon freshwater aquarium. In the beginning, the plants were thriving and growing well. I have added Coralife Plant Gro twice weekly per instructions on the bottle since their introduction. The floating water sprite seemed to grow quicker than the planted ones. Now I notice that the planted water sprite's leaves are drooping before they have a chance to attain full development. I am using an undergravel filter with two powerheads and an Aquaclear 500 power filter. The water temperature fluctuates between 78 and 82 degrees. I am wondering if the water sprites are lacking any minerals. Any help in this matter will be greatly appreciated.
-- Whitney Warden, Sr
New York, N.Y.

About the Author Scott Hieber has kept aquaria since he was 11 years old, "back in the metal frame days." He turned solely to planted tanks about five years ago, maintaining about a dozen at his home and workplace. In his enjoyment of living aquaria, he balances his penchant for simple, easy-to-maintain setups with a lifelong interest in things electric and mechanical. He serves on the Board of the Aquatic Gardeners Association. He has traveled to the Amazon to see tropical fish and aquatic plants in their natural environs. Originally from Southern California, Scott now resides near the New Jersey central coast. He says he went east "for the weather."

A. One should not be surprised if plants grow faster at the surface than submerged. Plants get carbon from CO2, and there is much more CO2 in the air than the water. In the air, CO2 is present at a few hundred parts per million (ppm). In aquarium water, it's about 3 to 8 ppm, unless one adds CO2, in which case it is probably about 15 to 30 ppm. So, CO2 is much more readily available at the water surface than below. Most aquatic plants, if they can reach up to the surface, will enjoy the plentiful CO2 in the air.

 

Water sprite (Ceratopteris spp.) is really a floating plant, and that is how it grows best. If you try to plant the roots in substrate, often water sprite will slowly degrade. Some of the species seem downright unhappy being submerged at all, while others seem to tolerate the condition, although not very well.

Try attaching some to  rock or driftwood with some thread near the water surface, and watch the change in growth once the plant reaches the surface. The difference can be amazing.

By the way, I'm not familiar with a Coralife water additive called "Plant Gro," but Hagen makes a product with that brand name. It does not contain any phosphate or potassium, so it should be used when those two nutrients are adequately supplied by some other means, either separately or from fish food (although fish food tends to add a lot of nitrogen and very little phosphate or potassium). A lack of macronutrients, nitrogen, phosphorus and potassium can cause a fast-growing, nutrient-hungry plant such as water sprite to show deficiencies quickly. In fact, the plant's introduction to an aquarium can soak up so much of the nutrients that it can create a deficiency where one did not exist before. As you add plants, especially ravenous ones like water sprite, you often need to supplement the nutrients.