by Chris (@shrimpery)
It would be a little ridiculous for me to claim to have invented a style of tank, but I think I’ve got the “pond tank” down to a science. Aquariums with areas of emersed plants (meaning the terrestrial forms of the plants typically used submerged in most tanks) have been steadily growing in popularity in recent years, but ‘pond’ tanks are a bit different from the current trend: they primarily use emergent plants usually found in outdoor water gardens. And unlike the emersed tanks I’ve seen, which often exclusively feature more leafy plants, I tend to focus on highlighting grassy emergent species, which are more rarely seen in the aquaria.
There are some special considerations to ponder when setting up this type of tank, so I wanted to present a little guide here to help. I’ve successfully created nearly half a dozen of these pond setups, and one of them- my ricefish habitat- has been up and running for over a year, with rewarding results. One big advantage of these tanks is that once they hit their stride, they require little maintenance compared to many other aquascaping styles.
Shallow tanks are well suited for this type of layout. I recommend a nice rimless shallow tank, such as an Ultum Nature Systems 60S. The surface area to volume ratio of shallow tanks ensures that gas is more easily exchanged between the air and the water; plants have better access to CO2, and animals have better access to oxygen. Additionally, more shallow tanks are more suited for creating banked slopes for the marginal plants to grow on; a very steep slope in a tank of normal height results in strange visual proportions and necessitates the use of a wasteful amount of substrate to create the embankment.
In terms of layout, I like to have an open area taking up the front quarter or third of the tank, leaving ample room for fish and shrimp to swim in the event that the rest of the tank becomes choked with vegetation. I prefer to use sand mixed with gravel at the front, for a cleaner look. The remainder of the tank- taken up by the slope- is made up of a skeletal framework of driftwood pieces holding up a mound of substrate (I recommend an enriched aquasoil such as Ultum Nature Controsoil) that slopes to the surface at the back of the tank. This slope often looks best if it’s primarily situated at one corner of the tank, leaving an L-shaped open area of water (as viewed from above). The severity of the slope, and the ultimate depth of water at the back of the tank will be determined by the emergent plants chosen to furnish the aquascape.
I always do lots of research on the emergent plant species I plan to use before constructing the tank. Above all else, I pay special attention to the optimal depth of the water level at the plant’s crown (the base portion of the plant where the roots meet the photosynthetic parts of the plant).
Some plants can tolerate water up to several inches above their crowns; other can handle less than an inch, or primarily prefer wet soil. Unlike most commonly used aquarium plants, which are truly amphibious, emergent plants are happiest with their lower portions permanently in water (or wet soil) and their upper portions permanently above the surface. Indeed, many of these plants will eventually die if completely submerged for long periods of time.
Additionally, the growth habits of specific plants must be considered. For example, you may not want an extremely tall plant that will look out of place in your aquascape or one that can only survive in high humidity. For research and inspiration, I’d recommend purchasing the Encyclopedia of Water Garden Plants by Sue Speichert and Greg Speichert, which contains growing preferences and beautiful photos of all sorts of plants that could be used in the pond tank setting.
Traditional aquarium plant species do work well in the submerged portions of the tank. At the base of the slope, I like to plant fine-leaved species, such as dwarf hairgrass, Monte Carlo (beware: Monte Carlo has a tendency to take over in this sort of tank), or other carpeting plants. Higher on the slope, a mixture of traditional aquarium plants or emergent plants may be used. Some good plants in this zone are those that can survive fully submerged but will convert to emersed forms once they break through the water’s surface.
A personal favorite for this middle ground is Sphaerocaryum malaccense, a true grass species native to southern Asia with small leaves growing from branching, structured stems. Underwater leaves can be a beautiful pink color under high light, and the emersed version of the plant can form a dense, bushlike clump with adequate trimming. This plant creates plenty of great nooks and crannies for fish and shrimp to hide in and is hardy and fast-growing once established. Java fern, buce, moss or other epiphytes may be planted on the parts of the driftwood scaffolding that stick out from the sloped embankment. Giant hairgrass (Eleocharis montevidensis) is an emergent grass that can tolerate deeper water and makes another great addition to this zone.
I like to have a small “dry land” area at the top of the slope for species that do best in wet soil, surrounded by an area of barely-submerged substrate for other marginal plants that like to have their feet wet. Some favorites for this zone include white top sedge (Rhynchospora colorata), which looks like a medium-sized grass with beautiful white flowers, and water celery (Oenanthe javanica), which looks like the leaves of actual celery plants but with bright pink accents. Both of these are good choices for the temperate conditions of an indoor ‘pond’ as they can tolerate cooler weather and have no special humidity requirements. Additional choices for the emergent area include aquatic mint, purple bamboo, Ranunculus species, and sweet flag (Acorus species), among many others.
In terms of additional equipment, all you need is a canister filter, an in-line heater (not necessary if indoor temps remain at room temperature throughout the year) and a good light fixture that won’t get in the way of the emergent growth. I’ve had success while using CO2 in pond tanks, but have been equally successful forgoing it, which I suspect can be attributed to the high surface area to volume ratio of the shallow tanks. Locating the tank near a window will help provide extra light for the emergent plants (and make for great photos)!
I’ve been enjoying the planted aquarium hobby since 2015, and having explored various tank styles, the pond tanks have been the most satisfying. Fish and shrimp love the extra cover that the emergent plants provide, and I’ve had lots of success with ricefish and neocaridina shrimp breeding in my pond tanks. Watching plants (often unexpectedly) change forms or spread to new areas of the tank adds additional dynamism, making the tank feel less like a prison for fish and more like an exciting little ecosystem. Hopefully, this guide will help you create a dynamic little ecosystem of your own!