Ecology of the Planted Aquarium

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ECOLOGY of the PLANTED AQUARIUM A Practical Manual and Scientific Treatise for the Home Aquarist by Diana Walstad
The purpose of the book is to explain: 1. how plants affect the aquarium ecosystem; 2. what factors affect plants; and 3. how the hobbyist can use this information to maintain a successful home aquarium.	Diana Walstad's Aquarium Fancy blue guppies in a 29 gallon planted tank
Table of Contents Summary Ch. I. Introduction
The introduction briefly describes the purpose and organization of the book and the characteristics of a 'healthy' aquarium. (5 references).
Ch. II. Plants as Water Purifiers (Click to sample this chapter)
In Chapter II, the toxicity of water contaminants- heavy metals, ammonia, and nitrite- to both fish and plants are discussed. I show how plants counteract those toxins to purify the water and protect fish. (75 references).
Ch. III. Allelopathy
Allelopathy, defined as chemical interactions between organisms, is most likely rampant in home aquariums. I present scientific evidence for allelopathic interactions between aquatic plants, algae, bacteria, invertebrates, and fish. I list specific chemicals isolated from a variety of aquatic plants and then list the organisms these chemicals have been shown to inhibit. Finally, I speculate as to how allelopathy might affect aquarium keeping. (96 references).
Ch. IV. Bacteria
Chapter IV classifies different bacterial processes in terms of their positive and negative impacts on the aquarium. Topics include the generation of plant nutrients, CO₂, and humic substances by heterotrophic bacteria. In addition, I explain how bacterial processes both create and destroy aquarium toxins. (54 references)

Ch. V. Sources of Plant Nutrients
Chapter V compares three potential sources of plant nutrients in aquariums- fish food, a soil substrate, and tapwater. I use a model aquarium to quantify the theoretical contribution from each source. I show that fishfood contains all elements that plants require and that soil abundantly supplies most micronutrients. I compare hardwater versus softwater as a nutrient source. In the final analysis, I discuss which of the three sources best provides each nutrient. (19 references)
Ch. VI. Carbon
Carbon is briefly described in terms of alkalinity and water buffering, and then more thoroughly as a plant nutrient. I show that the element carbon often limits the growth of submerged plants both in nature and in aquariums. I describe strategies that aquatic plants use to obtain carbon. Finally, I show how hobbyists can help provide their aquarium plants with more CO2. (34 references)
Ch. VII. Plant Nutrition and Ecology
Chapter VII describes the fundamentals of aquatic plant nutrition. Thus, the required elements and their chemical (nutrient) form are listed, along with each element’s function. Substrate versus water uptake of nutrients is discussed. I show that aquatic plants prefer ammonium over nitrates as their nitrogen source and why this makes biological filtration less critical in aquariums with plants. I discuss how the water chemistry of a plant's natural habitat influences its nutrient requirements. (75 references)
Ch. VIII. Substrates
Most hobbyists do not have soil substrates in their aquariums, which may be the main reason they have trouble growing plants. For a better understanding of this critical topic, Chapter VIII discusses the general nature of soils before delving into the even greater complexities of submerged soils. Finally, it describes how hobbyists can use soils in the aquarium effectively. (54 references)
Ch. IX. The Aerial Advantage
Chapter IX discusses the major problems that submerged aquatic plants face and why emergent plants do so much better. For the hobbyist, I describe how to promote aerial growth to optimize the aquarium ecosystem. (54 references)
Ch. X. Algae Control
Chapter X focuses on a major problem that many aquarium hobbyists have- tanks overrun by algae. Common methods that hobbyists use to counteract algal problems are evaluated. I then thoroughly discuss several additional factors that the hobbyist can use to control algae (the competition between plants and algae, lighting spectra, iron limitation, etc). Using this information, I show how hobbyists can successfully rid their tanks of algae without destroying the aquarium ecosystem. (39 references)
Ch. XI. Practical Aquarium Setup and Maintenance
In my opinion, planted aquariums are much easier to maintain than those without plants. Plants control alga growth and keep the tank healthy for fish without the drudgery of frequent water changes and gravel cleaning. In Chapter XI, I describe how I set up my planted tanks, which are both inexpensive and easily maintained. I also present my own guidelines as to fish, lighting, substrates, filtration, etc that the hobbyist can use to set up similar tanks. (4 references)	Diana Walstad's Aquarium *Young Tropheus duboisi* in a 45 gallon tank**

SAMPLE PAGES FROM THE BOOK

No's. 19, 27, 30, 100

Chapter II. Plants as Water Purifiers / 19
Additional Pages

Figure II-3. Cu and Zn Uptake by Leaves and Roots of Elodea nuttallii. Leaf or root sections were exposed to Cu or Zn (3.2 ppm) and then analyzed for metal accumulation in terms of dry wt. (Fig. 1 from Marquenie-van der Werff [48] redrawn and used with permission of Urban & Fischer Verlag Niederiassung Jena.)

Table II-7. Metal Uptake by Spirodela polyrhiza [51]. The metal concentration in the growth media and in the plants associated with 50% growth inhibition (EC50) was calculated after exposing 10 plants to 5-6 different metal concentrations for 4 days.

Metal	Metal Concentration Correlated with Growth Inhibition
Metal	In Media (mg/1)	In Plant Tissue (mg/kg)
Cadmium	0.089	773
Cobalt	0.14	590
Chromium	0.37	156
Copper	0.11	502
Nickle	0.11	1,290
Lead	3.7	6,730
Zinc	0.93	3,510

Giant duckweed (Spirodela polyrhiza). S. polyrhiza, like many other aquatic plants, can rapidly remove large quantities of heavy metals from contaminated water (see Table II-7). Plants are about 3 times bigger than ordinary duckweed (Lemna minor). Plant drawing from the IFAS [52].

Chapter II. Plants as Water Purifiers / 27
Additional Pages

In aquariums both fish and bacteria continuously release ammonium as they metabolize food and organic matter. Fortunately for hobbyists, most aquatic plants (and algae) vastly prefer ammonium over nitrates as their nitrogen source. This means that plants continuously sift the water for ammonium and its toxic component ammonia. Thus, I’ve never had problems with ammonia in my planted aquariums.
Hobbyists can protect fish from toxins by hard work, e.g., frequent water changes, gravel vacuuming, and enhanced filtration. However, given a chance, plants can purify the water naturally and effortlessly for the aquarium hobbyist. In my opinion, the ability of plants to purify aquarium water and protect fish has been woefully underestimated.

Comment from Fish Breeder. I thought you might like to hear about my experience using plants in my breeding tanks. For 7 years I have been breeding and selling Angelfish wholesale to the aquarium stores in the local area. I sell about 2,400 per month, so I always have at least 100 tanks stocked with 100 to 500 fry of different ages.

For many years I’ve used homemade canister filters and do 50% water changes twice a week. If I don’t change the water, the fish quickly (within a week) begin to show what I call ‘ammonia burn’. That is, their long pectoral fins look ragged and chewed off. Sometimes the gill covers are missing or the fish have ‘gill burn’.

A couple of years ago, by chance, I started adding Hornwort to some of the tanks. I’ve found that the fish in the Hornwort tanks need less care and water changes than in tanks without Hornwort. That is, the fish seem to have less tendency to get ‘ammonia burn’.

Because I’m happy with the results of keeping plants in the tanks, I’ve installed additional lighting in my fish room and have started adding trays of planted Val to other tanks.

Hornwort or coontail (Ceratophyllum demersum). C. demersum is a rootless submerged plant that is common in nature, but it is also well-adapted to aquariums. One successful fish breeder reported that the young fish showed less problems with gill and fin deformities when tanks contained Hornwort. Drawing from IFAS [52].

E. Carbon Sources for Plants

Lakes and rivers almost always have more CO2 than one would expect from just equilibration with air [9]. The extra CO2 is generated by decomposition (see pages 58-60). This CO2 can be considerable, especially since natural waters contain lots of dissolved organic carbon (DOC). Much of this DOC is in the process of decay, and therefore, is a potential CO2 source.

Many aquatic plants could not survive in nature without the CO2 provided by decomposition. Water in equilibrium with air contains 0.5 mg/1 CO2. Yet, many aquatic plants require much higher CO2 concentrations. For example, when CO2 levels were less than 36 mg/1, the moss Sphagnum cuspidatum was found either dead or dying [22]. And Callitriche cophocarpa and Ranunculus peltatus were found to be limited by CO2 in their stream environment containing 5 mg/1 CO2 [21]. Because these species cannot use bicarbonates, they depend on the CO2 released from decomposition.

F. CO2 in the Aquarium

CO2 for plants in aquariums is ultimately derived from fishfood and soil organic matter (see Table V-8 on page 88). Both of these sources require either fish metabolism and/or decomposition to turn organic matter into CO2.

If the hobbyist uses natural means (e.g., decomposition) to provide CO2, it is especially important to limit CO2 loss from the aquarium. CO2, because it is a gas, will be lost by all measures that increase air-water mixing, such as vigorous agitation of the water by spray bars, airstones, and ‘wet-dry’ filters.

Q. What are your feelings on CO2 injection systems. Do you feel they are worth the hefty price tag?

A. Whether a CO2 injection system is worth the money is a personal choice. I don’t use it, because I’m satisfied with my plants and aquariums.
Generally, aquarium plants will grow much better with added CO2. This is because CO2 is often the limiting nutrient in most aquariums including my own, if only because so many other nutrients, such as nitrogen and phosphorus, are so plentiful.

However, the down side is that with CO2 fertilization, your tank will require much more work. Not all aquarium hobbyists like the frequent pruning and weeding that is associated with CO2 fertilization. And because the nutrient carbon no longer limits plant growth, artificial fertilizers are often required. You will need to continuously monitor pH and KH to make sure that the alkalinity buffer is holding. If you have soft water, you will need to add sodium bicarbonate or calcium carbonate on a regular basis to maintain a KH that is safe for the fish. Even then, hobbyists occasionally report massive overnight fish kills from CO2 overdoses.

Also, there may be long-term effects on the substrate by CO2 fertilization. Thus, some hobbyists describe miraculous plant growth with their new CO2 injection systems, only to report an inexplicable collapse of their tanks a year or two later (see pages 48 and 140).

Questions about the book? Contact author at dwalstad@bellsouth.net

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