How To Succeed with Freshwater Plants, Without Really Trying
by a Petstore Staff Member

The first part in this series of articles will deal with the basic requirements of plants. The information in this article should not be considered as definitive, or scientifically absolute, but is rather intended as a good general working guideline that will enable the beginning freshwater aquarist to successfully grow an aquatic 'green thumb' with the least amount of time and trouble. Part two will deal with aquascaping and planting techniques, while part three will discuss the various species of plants themselves.

 Why plants?

Plants, in addition to their aesthetic value, provide important functions in a FW aquarium. They process and feed off of, the organic wastes that are created in the system, provide a lot of surface area for various micro-organisms, (which are a good food source for fry and small fish),  shelter, and territory markers, as well. They prefer to get their nitrogen directly from ammonia, and can also process nitrites and nitrates, to obtain their nitrogen. They also require, like every other group of living things, more specific items to continue their life processes, such as iron, and various minerals/carbonates.

Fine leaved plants, like hornwort (ceratophyllum) cabomba, ambulia, myrophillium, and floating plants with under hanging fine roots, like water hyacinth, water cabbage, etc., have been used as spawning 'receptacles' for many egg laying fish, both broadcast and adhesive spawners, (from goldfish and koi to zebra danios), for  centuries. Many cichlids, notably discus, angelfish, and other south/central American cichlids (usually the smaller and dwarf species, from the blue acara, to the ramirezi) spawn directly (also known as substrate spawners) on broad leafed plants, like the Amazon sword plant.

Plants provide different shapes, colors, and 'swimming zones’, and careful planning can achieve the result of your fish swimming in 'lanes' that you predetermine, if you wish. They also provide a much needed sense of security for many schooling and shoaling fish, like tetras and loaches, leading to better coloration, and more natural behavior .Plants will also compete with nuisance algaes for the same food source, leading to easier algae control/management.

Plants, in this author's opinion- do not help greatly with raising the overall level of oxygen of a closed system, as they 'breathe' oxygen and release CO2 at night, just like  fish. A good portion of the O2 released during the day into the system is simply 'canceled out' at night, by what the plants use up, as they respire.

Plants also help mitigate and stabilize certain water chemistry parameters, as a result of their natural life processes.

What do plants need to thrive?

Aquatic plants, just like their terrestrial counterparts, have some basic, simple, and easily provided needs/requirements:

1) Light of the correct spectrum and intensity (nothing about watts/gallon here, there is no such thing as watts/gallon, since gallons don't use light-more on this later.).

2) Food- usually in the form of fish waste and carbon dioxide (for the major nutrients, like nitrogen, carbon, sugars etc.) along with iron. (Iron is a necessary component of chlorophyll, without which the plant cannot photosynthesize.) Potassium is another important trace element, in addition to iron.

3) Carbonates (used to help build stiffening support structures inside the plant, e.g. leaf stems, branches, roots).

4) Oxygen, and Carbon Dioxide (for photosynthesis, and respiration).Provided for by proper circulation, and a Carbon Dioxide source, such as fish, or, a reactor.

Most of the commonly available plants will adapt to any pH value falling between 6.7-8.0, and a carbonate hardness range of 3 or 4, to 7or 8 dKh. (Degrees of carbonate hardness).Iron should be maintained at around .5-.7 ppm.

Food, light, and the proper water chemistry for their species, are usually determined by the conditions where the plants are originally found. Some plants prefer softer, more acidic water, some prefer harder alkaline water, and some just don't care. Most will adapt to a broad range of conditions, as long as minimal requirements are met, with only a few exceptions (for example, the Madagascar lace plant, which is extremely 'finicky').As most plants come from tropical areas of the world (along with the fish we keep), the temperature they should be kept at falls within typical aquarium temperatures.

Lighting:

Determining the correct lighting has nothing to do with gallonage of any kind (the same, by the way, holds true for saltwater/reef tanks). It has to do with the actual light requirements of the plant, (or coral) and the DEPTH (height) of the water column (water absorbs light radiation, so the deeper the light has to travel, the less will hit its target).Tint/turbidity can also be a factor (clear water allows more light transmission than brown, or green, water), as can regular house dust, surface film/scum. An excellent illustration is shown by comparing a 20gallon long, to a 20 gallon high - A 20 gallon high tank needs more watts of light than a 20 long, to achieve the same light intensity reaching the tank bottom, since it has a taller water column, in spite of them being of identical volume/gallonage.

There are many different types/styles/spectral outputs of light available today for the plant enthusiast. Any light with a spectral color (measured in degrees Kelvin) between 5500K and 10,000K will do just fine, regardless of whether it's fluorescent or metal halide, and a good general rule of thumb to use for fluorescents is one bulb, as long as the tank, for tanks up to a foot tall, adding one additional bulb for every six to eight inches of water column above the first foot. Low light plants, like java fern, some of the 'crypts', Anubias nana, will do fine with one less bulb for each 6-8" height increase above the first foot of water column height.

Power compacts are probably the best fluorescent style bulb for plants available for the hobby today, (http://www.marinedepot.com/aquarium_lighting_power_compact_powercompact__subindex.asp?CartId=) and metal halide is the absolute last word for top of the line lighting. When choosing PC fixtures, try to get bulbs that are as close to the length of the tank as possible, and configure the number of bulbs to the height of the water column as stated above, and you're good to go.

Keep in mind that fluorescent bulbs have a far less intense output near the ends of the bulbs than the middle, making a bulb that matches the length of the tank far more able to grow more plants towards the tank ends. PC bulbs are dimmer on only one (the pin) end.

Iron:

This is one of the most important trace elements for a planted tank, and one that is probably the most misunderstood. As stated above, iron is an integral component of the chlorophyll molecule-without it, plants cannot carry out photosynthesis, the process by which carbon dioxide and water are converted to food (sugars) using the energy contained in light photons. A lack of iron causes chlorosis-most easily observed on our lawns, causing grass to turn yellow, as it loses its chlorophyll. Iron is more easily absorbed by plants when it is in a ‘ferrous’ state, so choose a supplement that meets this requirement: (http://www.marinedepot.com/ps_viewItem.aspx?idproduct=SC5213)Cryptocorynes are an iron intensive plant, and are found usually growing in or near laterite beds (a clay type substrate with a very high iron content).

There are a few different ways to provide iron to plants-either via direct dosing into the water column, with a supplement like seachem's 'flourish' (http://www.marinedepot.com/ps_viewItem.aspx?idproduct=SC5213)or via a substrate high in iron, such as flourite,(http://www.marinedepot.com/ps_viewItem.aspx?idproduct=SC5231) or laterite.Iron levels should be checked weekly with a test kit. (http://www.marinedepot.com/md_viewItem.asp?idproduct=HG17835 http://www.marinedepot.com/md_viewItem.asp?idproduct=TZ6115 ).

CO2:

This is usually a more misunderstood subject than iron! CO2 will generally only be worthwhile to use, under very high light situations (until the plants are using up everything else they need at the maximum rate, the CO2 is not the 'limiting growth factor'-in other words, if the iron level is lacking, adding CO2 will not help the plants grow any faster, since the iron lack is the limiting factor).CO2 in excess can also cause another set of problems, from low pH to fish death. In my personal experience, it is the last method one should try to boost plant growth, after first eliminating the (possible) lack of the other basics.

Once a need or desire for CO2 dosing is established, it is very easy to administer, either via a bottle and regulator, or via some of the other unique dosing methods :(http://www.marinedepot.com/aquarium_freshwater_hagen_co2_natural_plant_system.asp?CartId= http://www.marinedepot.com/ps_viewItem.aspx?idproduct=AQ7531 http://www.marinedepot.com/aquarium_freshwater_sochting_carbonator.asp?CartId= )

Potassium:

Potassium is another fairly important 'major' trace element that plants need, in addition to iron. Active supplementation is generally not necessary. However, if all other 'growth factors' have been addressed, it may be prudent to add, before trying out CO2, to see if the level of potassium has become the 'limiting factor’. An excellent supplement is available: (http://www.marinedepot.com/ps_viewItem.aspx?idproduct=SC5193)

Compatibility:

As with fish, there are also compatibility issues with plants, though less severe.(and less traumatic for the hobbyist).The most obvious is 'chemistry' compatibility. If one is setting up a soft acidic water habitat, plants that prefer hard alkaline water would be an obvious poor choice. Some plants do not do well together, or in close proximity with each other, usually due more to growth patterns/speed than anything else. Keeping sword plants with certain other species can be sometimes difficult, if not impossible, due to the rapid and extensive development of sword plants' root systems (they literally can 'choke' other plants root systems).a single Amazon sword plant’s root system can completely cover a 20 gallon long's base in less than 2 months-I’ve removed large Amazon swords from tanks, along with 10 pounds of gravel, stuck to the roots, and the gravel was attached to roots all along the tank's perimeter!

Maintenance: (additives, parameters, cleaning gravel, filtration recommendations, etc)

Cleanliness is next to godliness, especially if you're a plant in an aquarium. Many are under the mistaken impression that leaving some 'gunk', 'mulm', bits of old leaves, small piles of fish poop, around the plants area is good for the plants-after all, it's fertilizer, right? Wrong! Plants should be kept every bit as clean as you'd like your fish to be, they can get bacterial/viral/fungal infections under dirty conditions, and prefer, for the most part, to absorb their food directly from the water column through the leaves. Keeping the gravel/substrate clean and well aerated is of prime importance. I've seen whole stands of crypts literally melt before my eyes due to severe and massive bacterial infections (crypts can, admittedly be more predisposed to 'catch' bacterial infections, but the main cause is usually plain old neglect/dirty habitat).

The substrates one can use for a planted tank vary, from 'regular' quartz gravel, artificially colored gravels, sand, to the specialty plant substrates, flourite, and laterite. A good ratio to follow is laterite to flourite at 1:4, or 1:5  (a slightly higher ratio should be used if combining laterite with inert quartz gravel.).

Testing the water chemistry at least once a week is recommended, until the hobbyist gets a 'feel' for what their system demands-in time, an observant hobbyist will be able to tell when and if dosing iron is necessary, just by looking at the state of his plants (much the same way some reef hobbyists can gauge a need for calcium/alk additives based on how their corals look and behave.).