COMPLETE AQUATIC PLANT GUIDE Part 1
Dr Mike Statham
Lots of people find it hard to grow plants in the aquarium, often after a few attempts they give up totally or resort to plastic plants, but it really isn't that hard provided you stick to a few simple rules.
This short guide is written from my own experiences from nearly 30 years of fish keeping including many successes (and probably many more failures) with aquatic plants and observing the growth of tropical aquatic plants in their natural environment. I don't claim my methods are the only ones that would work for you, but they don't rely on any expensive equipment or fertilisers, they are based on a real scientific understanding of how aquatic plants grow, and they work!
If this guide is useful to you please feel free to print or download it, but please observe that we retain copyright for all of the material included in this original article.
One of our plant collections.
Finally, I'm not being entirely altruistic, we sell plant collections here on Ebay which I personally think are the best quality and value for money you are likely to find anywhere, but at the end of the day you don't have to buy one if you don't want to, do you?
An entirely simple and natural planted tank here in our shop.
Five Basic Rules
- Pick plant species that are suited to the conditions in your tank (or arrange conditions in your tank to suit the species of plants you want to grow). This might sound obvious, but many people expect completely unsuitable plants to grow in their tanks and are then dissappointed when they die.
- Don't use any non-aquatic plants in your tank. Not as stupid as it sounds, a surprising number of the cheaper plants sold as 'aquatics' are nothing of the sort and are completely incapable of growing underwater. Some of these will survive for a while in your tank, maybe even grow a few roots, but ultimately they will all rot and pollute the water.
- Make sure you continously satisfy the three basic needs for your plants: light, nutrition and carbon dioxide (more about these later).
- To achieve rules 1-3 you obviously need to know something about the plants you want to grow! This kind of information can be found in good books, online... or you can buy one of our collections where we've done the hard work for you and picked plants to suit your conditions... Okay no more sales pitches.
- Don't expect plants to survive for long in a tank with plant eating fish. Yes, that most definitely DOES include 'Plecos'!
Light and Photosynthesis
- Plants need sufficient light to photosynthesise.
Without getting too technical, the process of photosynthesis is necessary for plants to grow and repair themselves. Without sufficient light (and healthy leaves) plants have to depend on their stored resources, when these run out plants will die.
In the tropics many regions have wet and dry seasons. In these conditions some plant species have adapted to store resources in a bulb over the dry season which can then feed new leaves when the rains return (e.g. some Aponogetons). Other plants can adapt their growth for being periodically emersed and immersed, growing different stems and leaves when in and out of water. Many of the popular aquatic plants come in to this category (e.g. Amazon Sword plants, Echinodorus). More about how these plants need to adapt to grow in your aquarium later.
With sufficient intensity of light your aquatic world becomes a forest.
In my experience intensity of light is much more important than duration when it comes to plant growth, although it is also important to consider the duration of time your lights are on each day. Aquatic plants only seem to be able to photosynthesise for about 8-10 hours a day, any extra illumination after this is just encouraging algal growth and both plants and fish need a decent rest period (night) between light periods anyway so it is not advised to light your tank for any longer. Investing in a cheap timer is a very good idea so you can fix a regular duration of lighting each day.
In general the higher the intensity of light in the aquarium the better as far as plants are concerned. But, beware many fish hate bright lights, one solution to this is to have lots of thriving plants for them to hide in when they choose.
There are many different potential light sources for aquariums, but the 1" (25mm) dia. T8 flourescent tubes are still the most popular. The smaller and more intense T5 flourescents are becoming more popular though and are a better option overall. Within the range of flourescent tubes for aquariums there is a huge choice. All have a limited effective lifespan, dimming slowly from the start, and it is worth bearing in mind that to get the best plant growth you will need to swap tubes about once a year.
Don't try to judge light intensity by the naked eye, your eyes are easily fooled, instead write the date when tubes will need replacing somewhere handy and stick to it.
Also according to the coating inside the glass, different types of flourescent light tubes emit different spectrums of light. This means some produce more light in the high wave length (blue) end of the spectrum, some in the short wave length (red) end and so on. Apart from making your fish look different this is significant because blue light penetrates water much better than red light, which is why everything looks blue underwater. But, blue light does not necessarily correspond to better aquatic plant growth overall and it is usually best to pick a tube with a spectrum mimicking sunlight (spread right across the spectrum) rather than one with a strong emphasis in any particular area.
Many aquatic plants grow long shoots or leaves towards the surface, float (either above, or below the surface), grow floating leaves (e.g. water lilies) and/or shed their lower leaves so that most of their growth is near the surface where the higher intensity of light is. This is a perfectly healthy and natural trait of true aquatic plants and must either be constantly fought against (regular cuttings) or accepted and designed for when planning your aquascape.
Aquatic plants that stay low and compact are few and far between, and usually grow best in extremely intense light and/or shallow tanks.
Light intensity can be increased by: increasing the number of tubes used, using reflectors (you can make a very cheap one by sticking self-adhesive aluminium foil in the lid behind the lights), and by cleaning or replacing dirty condensation trays. There also more powerful light sources available, but they inevitably cost more too.
The exact light intensity requirement of different aquatic plant species varies massively. There are a few that can survive on very little light (often considered the easiest to grow), and a great many that need more than an average aquarist can provide (that are usually considered hard for obvious reasons).
As a rule dark green aquatic plants need the least light, then light green, then yellow/brown/orange, and red or purple. This is the main reason so many 'colourful' aquatic plants are considered difficult to grow. In nature the more colourful aquatic plants generally grow in open and shallow water where there is no overhanging vegetation.
Nutrition and Substrates
- Plants require feeding like all living things.
Too many aquarists watch their beautiful plants starve and die without realising the cause.
It's obvious if you think about it, all plants (aquatic or otherwise) need feeding if they are to grow and repair day to day wear and tear. Without suffcient nutrition plants starve like any living thing.
Many aquatic plants will put down roots into the substrate if they can, many more, including all floating plants, prefer to have roots hanging in the water, and some prefer to use them to latch on to bogwood or stones. Some well adapted aquatic plants don't have 'roots' at all, such plants must collect all their nutrients directly from the water via stems and leaves.
The roots of floating Water Lettuce (Pistia stratiotes) can be 15cm long.
Roots usually serve to collect nutrients and must be able to pick them up from wherever they grow. Those plants that root into the substrate will be searching for food there, so it makes sense to feed these plants by fertilising the substrate. In a well established tank with fish this may well not be necessary as fish waste collects naturally in the bottom, but it is important not to clean the bottom of such tanks too vigourously or the roots will be disturbed and the plants starve from lack of nutrition. In fact well planted tanks require very little cleaning and are often best left undisturbed. Some snail species like to burrow in the substrate and these can perform a valuable task by moving the nutrients down through the substrate to the roots. Probably the best snails for this are the Malaysian Livebearing Snails also known as Malaysian Trumpet Snails (MTS), although these can also breed so fast as to be a pest. These are very often one of the species of live snail to come in with live plants, so it is rarely worth buying them.
Choosing your substrate is an important decision when designing a planted tank. This is especially important when a tank is set up initially as there is no build up of fish waste to feed the plants.
Gravel or sand are both fine for growing rooted aquatic plants, although the gravel must be of the finer type (e.g. 1/4 of an inch / 6mm). Some authorities claim fine sand compacts over time and hampers plant growth, although I have actually found fine sand is the perfect substrate for plant growth, even over ten years, or more.
It is possible to use silt, loam, peat, or river mud, for the substrate of a tank, but it tends to get stirred up too easily and clouds the tank (as well as blocking some filters). Probably a better plan is to place a layer of such 'rich' substrate under a layer of sand or gravel, and I have found this works very well with new tanks especially for Echinodorus sp. (Amazon Swords) which are very greedy and vigourous plants. Potting compost, or rich garden soil, work well, but be careful not to use any soil which might have had contact with any chemicals (e.g. weedkiller, pesticide, slug pellets etc...).
In densely planted tanks the plant growth may outstrip the capability of the fish to feed them. This is usually first seen as yellowish leaves, although some plants may exhibit stunted growth. In these cases it is necessary to add fertiliser.
I find fertilisers of the solid tablet type very useful, these can be buried near the roots of greedy plants and are easy to handle, they also don't pollute the water if used as instructed. Apparently rabbit droppings make ideal free fertiliser tablets, although I have never tried them. There are many professional brands available and all those I've tried seem to work well.
Liquid fertilisers need to be used in very small concentrations in my personal experience, and pick a brand without nitrates and phosphates if you don't want an algae bloom. They are potentially very useful for those plants that take their nutrition from the water.
It is worth noting that Undergravel filtration is not compatible with plants that are rooted in the substrate. The movement of water through the roots hinders their operation and causes plants to starve.
If you have the 'wrong' kind of substrate, or Undergravel filtration, all is not lost however, floating plants, plants growing on bogwood, and those of the 'moss' type that don't need to root can all be grown easily enough. Also if you want of grow some rooted plants you can plant them in individual flower pots or containers filled with the right kind of substrate for rooted growth.
Some authorities on growing aquatic plants recommend the use of an undergravel heating cable to ensure the temperature of the substrate is at least as warm as the water and the water doesn't stagnate in the substrate. These are not easy items to find and are very hard to fit retrospectively, but do seem to help growth of heavily rooted plants.
Carbon Dioxide and Respiration
- Plants need CO2 (Carbon dioxide) during photosynthesis AND O2 (Oxygen) at 'night'.
Most people know plants 'breathe in' Carbon dioxide and 'breathe out' Oxygen, but this is not really the full story.
When plants are photosynthesising they take in CO2 which is broken down in to Carbon (C) which is used for building and repairing tissues and Oxygen (O2) which is released as a waste product.
A nice view of an established planted tank with Hygrophila, Vallisneria and Nymphaea sp.
Aquatic plants have a real problem getting enough CO2, in nature, but most specifically in a majority of fishtanks. One way many aquatic plants have got around this problem is to grow floating or 'emergent' leaves (think of lilies and reeds) that can not only get more light than submerged leaves, but also get CO2 much more easily. Those plants that are forced to stay submerged have adapted to low CO2 (and light) levels, or have found other ways to get the CO2 they need, such as breaking down minerals in the water (Egeria sp. can do this).
This problem for aquatic plants is very often compounded by the way we set up our fishtanks. The CO2 and O2 dissolved in water exist in balance, when there is a lot of surface agitation, air bubbles, or water movement, the CO2 dissipates into the air and O2 is dissolved in its place. Of course from the point of view of fish, especially those crowded in a tank, having less CO2 in the water, and more O2, is a good thing. So most filters, air pumps, bubble walls, powerheads etc... are designed to get CO2 out and O2 in to the tank.
A great many fishkeepers would have more success with aquatic plants if they turned their filters down (or replaced them with slower ones such as air driven sponge filters) and removed all equipment causing aeration and water movment. In a planted tank the plants remove CO2 and produce O2, not the equipment.
Another complication is that as well as photosynthesising plants also respire slowly, taking in O2 and producing CO2, this carries on day and night. Although this process is slow the CO2 in a well planted tank (or pond) can build up overnight to critical levels for fish and other animals. This is one of the reasons fish are often seen gasping at the surface of a pond or lake on warm, still summer nights.
It is worth remembering that in a fishtank at night CO2 is being produced by fish, plants AND filter bacteria!
It is possible to run a simple aerator at night on a timer to counter this, but to be honest it is rarely necessary, and the plants quickly use up the CO2 produced overnight the following morning.
Plant growth can be encouraged with additional CO2, this is quite easy to achieve in an aquarium. All kinds of devices can be purchased to achieve this, from the cheap and simple through to the high tech and very expensive (or you can cheaply make your own using simple brewing equipment, sugar, yeast and water). In a CO2 rich environment, with sufficient additional nutrition and light intensity, plants will grow at an incredible rate. Such 'hothouse' aquariums are popular with those who want to produce a dramatic display of plant life, these conditions also allow many 'difficult' plants to be grown more easily.
Anyone adding CO2 to a tank muct be careful not to overdose, particularly at night, otherwise the stress on the fish may kill them.
A balance has to be struck and every aquarist who is considering CO2 addition must decide on their priorities. If the plants are the highest priority, and you wish to recreate some of the stunning planted tanks you can see online and in magazines, then high tech CO2 addition is going to make it easier to achieve. If, on the other hand, the fish are your priority, then CO2 addition should be used only in a very controlled manner, or not at all. It is a popular myth that aquatic plants need artifical CO2 addition to grow, many plants don't need it at all, and a great many were grown perfectly well long before CO2 addition became popular.
Obviously reducing daytime aeration should always be attempted before adding CO2, and anyone adding CO2 AND aerating their tank during 'daylight' hours is just wasting their time and money.
Chinese Fire Bellied Newt, a perfect denizen for a planted tank.
*Copyright M.Statham Last Trading Post 2006
*Permission granted for customers to print and download copies for personal use in original format only