COMPLETE AQUATIC PLANT GUIDE Part 1

by Dr Mike Statham : LAST TRADING POST*

Introduction:

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 I, and Last Trading Post, retain all copyright for all of the material included in this original article.

 One of our plant collections.

Finally, I'm not being entirely altruistic, I sell plant collections on my eBay shop ( http://stores.ebay.co.uk/Last-Trading-Post ) 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.

Four Basic Rules

1. 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.
2. 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.
3. Make sure you continously satisfy the three basic needs for your plants: light, nutrition and carbon dioxide (more about these later).
4. 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...

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 wither and 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 seasonally 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 one 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 bushy plants for them to hide in the 'shade' under).

There are many different potential light sources for aquariums, but most of us stick with the traditional T8 flourescent tubes because of availability and cost (although the smaller and more intense T5s are becoming popular and cheaper). Even within the range of T8s for aquariums there is a huge choice. All have a limited effective lifespan, dimming slowly from the day they are brought, and it is worth bearing in mind that to get the best plant growth you will need to swap T8's about once a year (max. 18 months).

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.  

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 spectrum light penetrates water much better than red spectrum light. This is why the deeper you dive underwater the more blue everything looks.

Light intensity attentuates (fades) much quicker when penetrating water than it does penetrating air, much of the light from most flourescent tubes is actually lost in the first few inches of water. When a tube produces more light at the blue end of the spectrum, the light gets to a greater depth, so there is more available for aquatic plants to use at a given depth. However, you must weigh against this that 'blue' light seems to promote certain algal growth more than 'red' light and 'blue' light can make certain colours of fish and plants look strange.

Many aquatic plants grow long shoots towards the surface, uproot themselves and float, 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 either extremely intense light 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.

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 then 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, but 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.

Most aquatic plants will put down roots into the substrate (gravel/sand/mud) if they can. Some floating plants prefer to have roots hanging in the water, and some rhizomes prefer to use them to hang on to bogwood/stones etc.. A few aquatic plants, such as those related to mosses and liverworts, don't have true roots at all. Such plants must collect their required nutrients directly from the water via stems and leaves.

 The roots of floating Water Lettuce (Pistia stratiotes) can be 15cm long.

Roots serve to collect nutrients and must be able to pick them up from wherever they grow. In general those plants that root into the substrate are the greediest and need the most feeding, 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. 3/8 of an inch). 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, or more, years. 

It is possible to use silt, loam, peat, or river mud, for the substrate of a tank, but I have found 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 thick layer of such 'rich' substrate under a 1 inch deep 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, or splotches of brown, although some plants may exhibit stunted growth. In these cases it is necessary to add fertiliser.

I find fertilisers of the solid tablet type the best. These can be buried near the roots of greedy plants and are easy to handle, they also don't pollute the water. 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 are not so great in my personal experience, although some of the new generation without nitrates and phosphates should be better. They are potentially very useful for those plants that take their nutrition from the water, but too many contain nitrates and phosphates (of which there is usually far too much in the aquarium already!) and just promote algae growth.       

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. These are not easy items to find (although they are sold here on Ebay), and are very hard to fit retrospectively. I can't say whether they work, or not, as I have never used them, but I have grown most species of rooted plants successfully without them.   

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.

Aquatic plants have a real problem getting enough CO2. This is because CO2 naturally escapes out of water over time and is rarely present in strong concentrations in natural waterways (although there are exceptions). 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.

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. Of course from the point of view of fish, especially those native to running waters, having less CO2 in the water, and more O2, is a good thing, and helps to keep them healthy. 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 naturally anyway.    

Another complication is that at night when the plants aren't photosynthesising they go in to 'reverse' respiring slowly by taking in O2 and producing CO2. Although this process is much slower 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!

Unfortunately, this is the one drawback to having a planted tank and is unavoidable. 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. 

It is possible to 'supercharge' plants by 'fertilising' them 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 such an 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. In these conditions aquatic plants that are otherwise 'difficult' can be grown and even some that wouldn't normally grow underwater can be kept alive.

In nature some such aquatic environments do exist, usually where there is a lot of bacterial activity, but such environments are rare and either devoid of fish life, or home to some very specially adapted species!

Anyone adding CO2 to a tank MUST turn it off overnight, 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 much easier. If, on the other hand, the fish are your priority, then CO2 addition should be used in a very controlled manner, or not at all. It is a popular myth that aquatic plants need CO2 addition to grow, but many plants don't need it at all, and a great many were grown perfectly well long before CO2 addition became popular.

In my opinion it is more important to reduce aeration than it is to add CO2, and anyone adding CO2 and aerating their tank during 'daylight' hours is just wasting their time.

Cont. in pt 2.   http://reviews.ebay.co.uk/Growing-Aquatic-Plants-in-the-Aquarium-pt-2_W0QQugidZ10000000002357748      

 Chinese Fire Bellied Newt, a perfect denizen for a planted tank.

*Copyright Dr M.Statham Last Trading Post 2006

*Permission granted for customers to print and download copies for personal use in original format only