Painting an aquascape on the 20-gallon tank is similar to painting on a smaller canvas. It offers the essence of intimacy and a real challenge. But it also provides the reward that is so typical of 20-gallon rigs. I have spent many years working with hitting the sweet spot of various tank sizes, but I keep coming back to this particular tank. My still life with water in the 20-gallon tank is large enough to afford real artistic vision and to let the aquascaper’s imagination run wild. Thanks to the elements of balance and precision that hardscaping demands in every detail (and pushing against every instinct to go big and bold in the amount of substrate), the work in this tank also somehow allows for, and really demands, better artistry and a little more patience than many aquascapers might be used to asking of themselves.
One of aquascaping’s most insightful lessons has been that the size of a tank determines not only which varieties of flora and fauna can be housed within, but also the specific aesthetic or vibe of the entire setup. When working with something like a 20-gallon aquarium, you come to appreciate that every single cubic inch of space is valuable real estate. Anything you place inside has to earn its keep. It’s got to serve some kind of aesthetic purpose, whether adding an illusion of depth, presenting something as a focal point, or in some way maintaining the visual balance of the whole thing, since by now, I’m sure you realize, the plants, rocks, branches, and even fish have to maintain harmony and semblance of “nature” inside a pretty small space.
My first 20-gallon setup had a vibe that was heavily inspired by the Dutch aquascaping school of thought, with which you may also be familiar.
Aquascaping is very much like the art of landscape design. You can try to superimpose a concept on nature, but it takes a skilled aquascaper to make that look natural. At the same time, you want a look that both dominates and does not dominate—an appearance that intrigues viewers without making them wonder whether you have the right plants in the right places to achieve effective growth. You don’t want to make them think aquascaping is a sort of secret handshake. After I graduated, I was awarded the reorganizational equivalent of a fellowship that allowed me to travel around the country visiting universities.
The first stop was in an office with a department chair who doubled as a successful public speaker. On the office shelf were aquascaped tanks that looked intriguing without any clear reason why they did. Also, they were set up in a way that made it quite clear you could not tell from looking at them whether or not what was going on inside was any more sustainable than a comparable hacky-sack workshop.
I generally favor a combination of species when I consider which plants to place in a 20-gallon aquarium. I enjoy species that afford me a variety of textures and growth patterns. I like the contrast between primary plants that grow slowly, like Anubias or Cryptocoryne, and those that grow quickly, like Rotala or Ludwigia. This combination is really key in maintaining quality water, while also providing a pleasing visual to my eyes.
One of my very favorite sets of plants in a 20-gallon aquarium is a carpet of Eleocharis acicularis (dwarf hairgrass) paired with taller, mid-ground plants like Rotala rotundifolia. There is something about the visual gradient this tank creates that moves from the soft, lush carpet of hairgrass to the delicate, wispy stems of Rotala. I could watch that both of those species inhabit 20-galllon aquarium all day!
Another important factor in selecting plants is light. From my experience, it’s much safer to set up a low-light aquascape than a high-light one. Hardy plants like Java fern, Anubias, and various mosses thrive under low light and don’t require high-tech equipment like CO2 injection. If you want to keep things simple, these are the sorts of plants I would stick with. If you’re trying to create an aquascape that’s comparable to something you might see in a highly designed Nature Aquarium, then you’ll need to go with high-light plants to create the same sort of stunning visual impact those sorts of setups achieve.
However, in a 20-gallon tank, assuming you want to maintain something comparable to a “balanced ecosystem,” avoid fast-growing plants like I did with my Hemianthus callitrichoides and with Alternanthera reineckii. A good substitute for high-light, fast-growing plants is to use plants like Carex, which will maintain the same appearance under low light, and with much less fuss.
A cherished memory of mine revolves around a biotope aquascape I designed at one time, a 20-gallon tank, to render the natural habitat of the Amazon blackwater river. I wanted to recreate something special—my version of the warm, tannin-rich waters of the Amazon Basin, where the breakdown of organic matter makes the water appear almost tea-colored. For this blackwater setup, which I was simultaneously moodily lighting and watering each day to create a desirable brackish zone, I was using driftwood and very little leaf litter to tint the water. I placed small schooling tetras and corydoras catfish as my only blackwater inhabitants in front of an aquascape that had almost no visible foreground to speak of because I was using basically no plants.
When it comes to hardscape, I learned to pay close attention to how hardscape materials affect water parameters. For example, Seiryu stone and some other types of rock can significantly raise the pH and hardness of the water. In one of my smaller aquascapes, a 20-gallon tank, I made the mistake of using too much Seiryu stone, and over time, I began to notice that the pH of the water was climbing. I had to remove a lot of what I had added and replace it with more inert materials, like lava rock, which doesn’t do much of anything to change water parameters.
However, this experience taught me a couple of important lessons: Test everything! And don’t be afraid to experiment in a smaller tank first before committing to hardscape or planting decisions in a larger one.
The 20-gallon tank gives me a lot of options for using odd hardscape elements. I’ve worked with several kinds of driftwood, including spider wood, which is quite unlike anything else. It has an appearance similar to petrified wood but is much lighter and thus very easy to work with. Sculptural and twisted, it’s hard to describe just how insane the shapes that spider wood takes on are. I can see why some people would shy away from using it, given that it doesn’t look like what most people think of when they picture wood in a tank. This last bit, however, makes it wonderful for giving a serious wow factor to the kinds of natural spaces I picture creating with my aquascapes.
I derive great pleasure from adding floating plants to my 20-gallon aquarium. Amazon frogbit and duckweed are two particular favorites of mine. They do a fantastic job of softening the quality of light in the tank, allowing for a more tranquil, natural appearance. However, what has caught up with me is not the tranquil, natural appearance of these plants but their rampant growth. I severely underestimated how fast frogbit could spread. After only a few weeks, my surface was almost entirely covered with this plant—an effect that made my tank appear like an urban jungle. More lighting obscurity is bad for any plants/animals in the tank.
Still, I have thinned out the surface. What I have now is a dense “urban jungle” effect at the bottom coupled with an almost-surface plant connection spanning across the surface!
My thoughts on stocking a 20-gallon aquascape with fish always revolve around the balance of plants and fish—a necessity to avoid the catastrophe of an aquascape thrown off balance by overstocked or incompatible fish. For this size tank, I’ve learned that the ideal choice is smaller, community-friendly fish. They bring a certain amount of life and interest to a space, but they do so without disrupting either the plants or the hardscape, which is such a fine line to walk when making aesthetic decisions about fish.
For a 20-gallon aquarium, the Neon Tetra is one of my top choices. These little jewels are vibrant and peaceful, and their schooling behavior adds an incredible sense of dynamism to the aquascape. A school of 10-12 Neons swimming against a green background is a sight to behold. Working with a similar theme, I’ve also had success with Harlequin Rasboras and Ember Tetras, both of which are small, warm-colored schooling fish that occupy the space without overwhelming it. In one of my setups, I combined Ember Tetras with Corydoras pygmaeus, a very fitting species of dwarf Cory for my 20-gallon tank.
The busy Cories were perfect for stirring up the bottom as they darted through the plants and around the driftwood, while the Tetras settled into the multi-layered tank as a middle-and-upper level school.
Creating a “nature aquarium” in my 20-gallon tank is one of my fondest experiences. It was the first tank I set up where I furnished it with what my then-budding aquascaping skills allowed. I stocked the tank with Amano shrimp and Otocinclus catfish, both of which are superb at keeping any algae from interfering with the delicate layout I had constructed. Algae is a sneaky beast, creeping in during the most favorable of conditions—strong lighting, high CO2 levels, and a wholesome level of nutrients for what are otherwise gorgeous aquatic plants. The combination of algae eaters and careful management of the tank’s lighting and nutrient load has always allowed me to maintain a pristine aquascape.
Another wonderful aspect of a 20-gallon aquascape is that you can keep shrimp. They not only serve as a great means of keeping the tank clean, but they also fulfill the same role as fish in terms of adding a sense of life and movement. Indeed, there’s a spectacular amount of variance between different shrimp species in terms of coloration, size, and behavior, so you can keep shrimp in a 20-gallon tank and have a different look among every “level” of the tank (i.e., surface, mid-water, and bottom) if you want. I’ve always found that peaceful tank mates, such as Tetras and Rasboras, coexist exceptionally well with shrimp.
One of my unforgettable aquascaping endeavors was when I attempted an aquarium based on the Walstad Method. This isn’t the typical aquarium set up. Instead of using really high-tech methods to make sure the water is just right, or even using plants that filter the water and make it very safe for fish, this kind of aquarium depends on a natural balance. It’s not unusual to have fish and plants create some sort of balance in an aquarium, but in this one, I relied on just a few hardy fish and some very minimal “high-maintenance” plants, using them in conjunction to create a system in which these not very robust plants survive just fine in a “nutrient-rich” environment.
This is a 20-gallon aquarium set up to thrive with mostly hardy plants.
If you relish the opportunity to exert control over your aquatic landscape, a high-tech setup can yield just as satisfying results in a 20-gallon tank. I have found that using pressurized CO2, high-output LED lighting, and a careful nutrient regimen can push even the most demanding aquatic plants to realize their potential. One of my favorite scenes in a high-tech aquascape involves a lush carpet of Hemianthus callitrichoides (the dwarf variety of baby tears). Grueling as it was to keep that scene alive with daily injections of CO2 and round-the-clock lighting management, the payoff was breathtaking—I mean, really, if you could see this, you would be holding your breath.
High-tech setups in a 20-gallon aquarium bring their own set of fresh challenges, the most delicate being CO2 levels. In a smaller setup, it’s all too easy to overdose the gas, leading to stressed fish and crazy pH swings. Poor Neon Tetras! When I was pushing them to be great aquascaping plants, I had to get real with my CO2 experimentation. I remember doubling down and really trying to optimize my precision; my targets were 30 ppm of CO2—that’s a 150-gallon-a-breath underwater world for my Tetras.
Of course, by “my” Tetras, I mean the ones I had and loved, watching them do what they do best—be very “on stage” in the aquatic theater that is a living room. Failing to meet their needs could have made former product-support calls sound like life-saving missions given a doctor’s real-world persona.
Finding a maintenance rhythm for a 20-gallon aquascape takes work but pays off handsomely. There is a lot that can go wrong with a tank this small, and I’ve seen firsthand how things can go bad in a hurry. This is why I try to keep my weekly maintenance routine as close to ideal as possible, with only water changes and plant trimming occupying my mind for 30-45 minutes each week. Like a good melody, the week-to-week pattern of these tank chores has been easy for me to get into and has felt great, too, both aesthetically and viscerally, as a way of keeping the tank alive and healthy.
Professor Margot Gerritsen would call that the “understanding essence,” with which I have been getting better over time.
Managing algae is a continual necessity in a 20-gallon aquarium. Even with the algae-eating tandem of Amano shrimp and Otocinclus fish, it can sometimes feel as if algae are winning the war. I’ve used a multi-pronged approach, combining almost weekly water changes, a light cycle that brings the total daily duration to between 10.5 and 11.5 hours (this is what works for my system), and direct, manual treatment with liquid carbon to afflicted areas and plants as a means to keep the algae at bay. One of the best pieces of advice for aquascapers that I can share is to be proactive in controlling algae; it is far easier to stop an algae bloom before it starts than it is to put a stop to one that is already underway.
To sum up, a 20-gallon tank allows for good aquascaping because it’s a nice balance of room to work and space constraints. I have recently discovered the beauty of working at this scale, and it’s something I am quite taken with now. You can easily keep 20-gallon tanks as either low-tech, self-sustaining aquariums or high-tech setups that, far more often than not, require a fair amount of daily maintenance to keep in check. There’s two opposite paths to take here, and I seem to flit back and forth between them quite irregularly.
