We might not need to worry about watering our aquarium plants, but surely they have some needs? Tom Ackrill explains.
WE’LL ALL REMEMBER those lessons at school where we learned all about plants: photosynthesis; the electron transport chain; the xylem and phloem; and all the other terrifying details stored somewhere in the back of our brains. Little did we know in those days that we’d end up keeping aquatic plants and having to come back to those little nuggets of knowledge.
All plants—aquatic or otherwise—rely on a variety of nutrients, and the absence, excess, or shortage of these can lead to problems. The upside is that quite often our plants will tell us what the problem is, as long as we know to look out for the signs.
Nitrate
One of the three macronutrients—the three big hitters of the plant world without which any hopes of healthy lush growth will be quickly dashed. Nitrate is usually present at some level in tapwater (although not always), but as luck would have it is also the final product of the nitrogen cycle, as the end result of ammonia from fishes and other organic waste being converted by filter bacteria. This means that on some level this vital nutrient is being produced ‘in-house’ within the aquarium, although often not in sufficient quantities.
Nitrate is used by our plants as a source of nitrogen, from which various proteins are formed to allow the plant to grow. Without this available in plentiful supply, growth will be poor, if at all.
The downside is that high enough levels can be toxic to aquarium fish, so it’s not a case of the more nitrate the merrier. For the healthy keeping of sensitive fishes, some aquarists aim to keep levels below 20ppm, while the typical community tank shouldn’t have nitrate in excess of 50ppm. However, in a high-energy layout with intense light and added CO2, some plants may struggle (with leaves turning yellow or clear) at levels below 20ppm, and so a consistent 30-50ppm may be required for hungrier species.
Phosphate
Perhaps the most misunderstood of all the plant nutrients, phosphate is often blamed for causing algae issues when present in any meaningful quantities. Indeed, there’s a plethora of products on the market for stripping this vital nutrient from water, but this really isn’t the baddie it’s made out to be.
Phosphate is a source of phosphorous, which gets used extensively by plants. First of all, it’s a vital component for making new DNA—if you picture a double-helix
