MAKE LOW-TECH WORK FOR YOU
Daunted by fertilisers and carbon dioxide? Danny Verboekend suggests it needn’t be so difficult to set up an algae-free, low maintenance aquascape at home.
However, this also leads to a rapid boost in the amount of organic waste formed by the plants, which in turn begins to reduce their growth rate. Once the growth rate is lowered again, the pearling ceases. In short, plants don't seem to like standing in their own pee.
So now we have the general picture: in order to maximize plant growth, we need strong lighting, plenty of nutrient-rich aquascaper soil, liquid fertiliser, dosing of CO2, and — and this is the important bit — loads of water changes. In a clinical sense, these all represent the core ingredients of high-tech aquascaping.
Going wrong
So, what does aquascaping ‘failure’ look like?
Generally speaking, two (related) types of failure occur. The first is that your freshly-purchased plants do not grow or even start to slowly die and melt away, while the second is the abundant and persistent formation of different types of algae. Although subject to ongoing debate, both the melting of plants and algae formation can be related to an imbalance in the items we’ve just looked at: fertilisers, gas content and water changes. As with most good things, a sense of balance is implied.
Back to basics
Alrighty then, with the basics laid out, let’s face the last key question. What actually is ‘low-tech’ aquascaping? Generally speaking, a variety of approaches may claim to be low-tech. Still, most options feature two common aspects. The first is the absence of any additional CO2, while the second is a reduced rate of water changes (as compared to a high-tech aquascape). On this second point, it’s common for a low-tech tank to receive a waterchange no more frequently than two weeks apart (and often much less frequently than that). Importantly, any tank without added CO2 has a lower potential growth rate for plants compared to one that does. But on the other hand, the requirement for the considerable water circulation necessary for CO2-powered tanks — up to 10 times the tank’s volume every hour — is less critical. With CO2 injection, flow is essential to ensure that the gas is distributed evenly throughout, which for a ‘CO2-free’ set-up isn’t an issue. With that out of the way, let us now finally discuss two fundamentally different scenarios of low-tech aquascaping. One where we start with a lusciously planted aquarium and only liquid fertilisers in the water column, and the other in the same tank with fertiliser present only in the soil.
Where to fertilise
In the case of fertilising only the water column, getting the light intensity right is vital, as using too much of it can easily turn the tank into an algae-infested mess.
ABOVE: Diagram of a high tech system with liquid and soil fertiliser, a low tech system with only soil fertiliser, and a low tech system with only liquid fertiliser.
This is because of the imbalance between high levels of nutrients in the water column and low amounts of CO2, and is compounded in a tank where water changes aren’t carried out regularly, and plant growth is further inhibited by their own ‘pee’.
In order to calibrate the planting ecosystem to a low level of CO2, we should reduce the growth rate, which means reducing light intensity. Doing so will concomitantly enable us to get away with a lower amount of water changes.
Most aquarium kits these days provide high-intensity light systems, making, especially for low-tech aquascaping, some degree of control over the lighting intensity a necessity. LED-based systems, for example, commonly feature high intensities of about 0.3 W/L.
For a water-column fertilised low-tech system, my own experience has shown that this is best reduced to closer to 0.1W/L. If the amount of nutrients is then also reduced by a similar factor as the light intensity, a more balanced (and more likely algae-free) system is obtained. In tanks where plants are solely fertilised through the roots via soil fertilisation, the water column should be largely free of nutrients. This represents a complete game changer as, without nutrients, algae should not stand a chance.
Under high lighting, the challenge in this scenario is to ensure that no excessive amounts of nutrients get into the water column, and so to start, any melting of plants and organic detritus should be removed asap from the tank.
Setting up can be tricky as large amounts of nutrients may be released from the fresh aquascaping soil — every time the soil is
disturbed, some nutrients escape from it into the water. With this is mind, any uprooting of plants during maintenance should be followed by large water changes.
Light fish stocking is also recommended in order to keep the (fish) waste-derived nutrients in the water column low.
Further considerations
Both water-based nutrient and soil-based nutrient low-tech aquascaping approaches have profound consequences on several other aspects.
In terms of plant choice, the two scenarios favour different types of plants. For example, using the water-fertilised set-up, a lower light intensity implies that many mediumto-high demanding light species may not thrive (such as Staurogyne repens and any of the carpeting plants). In addition, the growth rate of heavy root feeders (such as Vallisneria and Amazon swords) may be reduced due to the limited ferts available in the soil.
In contrast, when fertilising only the soil, plants taking their nutrients from the water column (such as ephiphyte plants like Java ferns, Anubias and
Bucephalandra, as well as floating plants and certain fast-growing stem plants) may suffer.
In each of these cases, long term ‘tank syndromes’ may occur. In the case of the water-column fertilised systems, waste of fish and plants can start to penetrate the soil over time, giving rise to the eventual release of nutrients for the roots. This suggests that a new tank may slowly become more suitable for root feeding plants over time. In contrast, the soil of the rich soil-fertilised system may eventually become depleted of nutrients, giving rise to a lower growth rate of root feeders in time.
Make it happen!
With all this wisdom, let’s have a go at making the ultimate beginner recommendation for a successful one-hourly maintenance per week low-tech tank.
Let us consider an aquarium of about 50-100 l. For this size initial heavy stocking with plants will not be overly expensive and at the same time water changes will not take too long. Also, the height of the tank should enable you to still grow most sizes of plants. Make sure the LED-based light unit can be controlled in intensity and set it at about 0.1W/L, and keep it this way for a cycle of eight hours. But don't put the lights on just yet!
With that arranged, add a proven plant soil (at least 10cm deep), add your hardscape, fill with water, and run your tank in the complete darkness for about three weeks. This helps to cycle your filter and soak up any excessive nutrients released by the soil or hardscape in the water.
After this period, empty your tank to just above the soil, and purchase your plants. Focus only on ‘easy’ plants and include at least 50% of fast growers.
Suitable plants include: Dwarf sagittaria, Sagittaria subulata (fast growing); Vallisneria (fast growing); Anubias; Java fern, Microsorum pteropus; Amazonian swords, Echinodorus sp. (fast growing); and perhaps some mosses.
Now, for the best part, release your inner ‘artiste’ and ‘scape these plants and hardscape into an unprecedented underwater Babylon garden. Finally, add some surface plants, making sure that never more than 30% of the surface is covered (in order to maintain sufficient light for the submerged plants).
Finally, add fertiliser to the water column at a dose of about a half as compared to a high-tech system (for example based on values for the EI method) and replace 50% of the water once a week for 1 month, followed by light fish stocking.
Then, and only then, we arrive at the final destination — a beautiful CO2-free aquascape of which we change 50% of the water only once every two weeks. Good luck!
CATFISHES DISPLAY a vast diversity in morphology and diets, and dominate the planet, inhabiting all the continents except Antarctica. We have catfishes in Europe (like the Wel’s catfish, Silurus glanis), Asia (like the families of Bagridae, Pangasiidae, and Siluridae), Africa (including the Mochokidae and Clariidae,), North America (Ictaluridae) and the staggeringly popular catfishes of South America (such as the Loricariidae, Trichomycteridae, and Callichthyidae). There are even marine catfishes such as the venomous Plotosus lineatus.
Across the many families, catfish size ranges from miniature fish not much over 1cm to absolute giants of at least 300cm and potentially weighing hundreds of kilograms. With such a diverse morphology it stands to reason that not all catfish have evolved to eat the same foods, and within their ranks you’ll find a range of feeding adaptations including parasitism, carnivory, herbivory, detritivory and omnivory.
Plants, bacteria, fungi, protozoa and bacteria make up an important part of any ecosystem, and freshwater is no exception. A large number of fishes exploit these plentiful resources, and these are referred to as the herbivores.
Within herbivory you can divide even further into the algivores (that eat algae), frugivores (fruit), folivores (leaves) and granivores (seeds). Fungivores, species which feed on fungi could be considered herbivores, while those fish that specialise on decaying matter are known as detritivores.
Many feed on structures known as periphyton, a complex material that grows on submerged surfaces and contains a mixture of algae, bacteria, protozoa and microbial life. Fish diets can be a little more complicated, as the occasional invertebrate — creatures such as sponges, bryozoa and rotifers — can make their way into their diet by also inhabiting the periphyton.
International catfish tastes
When it comes to catfishes there is one group that is largely known for exploiting a herbivorous diet: the Loricariidae of South America, known colloquially as the plecos. The majority are either algivores or detritivores although a few are omnivorous or carnivorous. With so many species found in overlapping ranges, each of them specialises, partitioning their dietary niches.
Fish diets are reflected in their morphology. For example, a rasping mouth with numerous fine teeth will be oriented towards feeding from a surface, likely on periphyton.
When it comes to the Loricariidae, or plecos, there are misconceptions about which genera eat what. Out of the subfamily Hypostominae, which contains the most common species labelled as plecos, those in the genera Scobinancistrus, Leporacanthicus, Pseudacanthicus, Lithoxus and Exastilithoxus are, as far as we are aware, true carnivores.
Hypancistrus, Peckoltia and similar genera are omnivores/detritivores.
Panaque, Hypostomus, Panaqolus and
Lasiancistrus heteracanthicus tend to be detritivores who feed on microbes that decay wood. Baryancistrus, Ancistrus, and Chaetostoma are herbivorous, and the majority swing towards being algivores.
In Africa a few members of the family Mochokidae eat aufwuchs, such as Euchilichthys guentheri, while Synodontis brichardi and Synodontis schoutedeni will consume algae as part of an omnivorous diet. If you look carefully at these two Synodontis they also have rasping mouthparts suggesting that they also graze on some resource growing on a surface.
Healthy gut, healthy body
The diet of a fish is reflected in the digestive tract — the stomach and the intestines. For example, longer intestines suggest that a fish has evolved to ingest food that takes longer to process, and that’s usually a herbivorous diet. By contrast, a large stomach and short intestine hints at a carnivorous fish.
If we look into their molecular physiology, all organisms generate proteins known as enzymes, and these are used to break down their food. These enzymes have evolved over thousands of years to break down a specific part or parts of a diet, and where an animal has not evolved the enzymes to process specific parts of a diet, that diet will not be processed by the digestive tract. The unprocessed food will either pass straight out or it will result in fluid and gas production, bloat and digestion issues.
Inside the intestines there also resides a variety of bacteria and archaea directly involved in the digestive process. Like enzymes, these bacteria have also evolved over generations to feed on specific aspects of a fish’s diet — some deal with vegetable matter, others with flesh, and so on.
Feeding a herbivorous species on a carnivorous diet (for example, foods high in fish/krill/insect meal content) will likely not provide suitable levels of nutrition as it will not be digested.
Fundamentally, malnutrition will likely occur where any herbivorous species cannot break down carnivorous food.
What to look for
Labels on fish foods can lead to confusion. For example, a food labelled as a ‘pleco diet’ must be herbivorous, right? After all aren’t members of the Loricariidae
(plecos) herbivores?
Well, no, and therein we find a problem. Marketing a veg-based food as suitable for all plecos ignores the presence of omnivorous and carnivorous species — all of which are plecos.