As aquarists mature with their hobby they often look to change, diversify or specialize their interests in what they are keeping. This is usually done to help them learn and maintain interest. Often it is just because something they saw got them very excited and they wanted to try it too. This series of articles is about one of those alternative interests, specifically aquatic horticulture.
Plants in the aquarium are often passed by as many aquarists tend to believe that they are too difficult to keep alive let alone reproduce. As compared to fish, if properly cared for, they are just as easy but have different feeding requirements than fish do. It is the belief by most hobbyists that you should just be able to plant them into your tank and they should grow. You would not expect every fish you see available to be flopped into a tank and thrive on flake food, some would likely starve to death on that type of diet. Essentially the aquarist that brings home a plant and expects it to grow and grow without proper food is likely to starve the plants.
As fish require nutrition in different forms, we as responsible fish keepers try to give them a varied diet whenever we can to keep them happy, healthy and robust so that maybe we can get them to spawn. We feed things that we can recognize as being food like Frozen Brine shrimp, Bloodworms, an assortment of freeze dried stuff, flakes and whatever living foods we can lay our hands on. Some of us even go out of our way to provide variety and make preference of feeding live foods as we know that this is desired by our fish. Although plants need to be fed as well, we are not as able to recognize the food they require. This is in part because what they feed on is not in a commonly recognized form. It is often dissolved in the water and we are unable to actually watch them feed so we do not know if they are immediately satisfied with what we have provided them.
Plants feed on raw chemicals or at least very nearly raw and it is in this form that we need to feed our plants. It would be helpful if we could just run down to our local fish store and pick this stuff up. This is usually not the case though. Few stores, if any, are equipped to fill bottles of CO2 (Carbon dioxide). Iron in liquid form that is not a pain to use is tough to come by and the clay like laterite that is put into the gravel bed can be a mess if not applied properly or put into use when the tank is set up. Most of the other types of plant foods are usually found in large enough amounts in our tap water that we really only need to concern ourselves with CO2 and Iron (Fe) feedings. The one other food, if that is what you wish to call it is light.
Light is not actually a food but if the plants are to be able to feed then light must be provided. With only a few exceptions, the more light that you provide, the better your plants will feed. This directly promotes good, swift, growth in your plants.
To administer these foods properly does take some different equipment than you would normally use for a fish tank. First to consider is light. Light should be provided with at least 2 strips of light for the length of the tank you are going to use. Just for the sake of reference, we will use a 55 gallon tank as our make believe set-up. On a 55 gallon tank, which is four (4) feet long, you should place at least 2 four foot long fluorescent tubes. These do not have to be special high output or anything like that, a standard shop light will work. You can also use 4 - 2 foot tubes and fixtures but the 4 footers will be easier to get a hold of and cheaper.
Next, and although not totally required, if a way to administer carbon dioxide as a gas into the tank. Some may suggest that CO2 is not needed to be successful but over the long run it is like saying that you do not need water either. CO2 is an essential element in the growth of the plant. There are few other sources that can provide this gas that is better, more efficient or cheaper than carbon dioxide injection.
To set up this injection system you will need a bottle of carbon dioxide gas, an outside canister filter and some form of gas regulation system. The bottle of gas may be the easiest choice here as there are several places that will rent you the bottle and for a modest fee, will refill it when it gets empty. This fee ranges from $700 to $1200 and the deposit on the bottle can range form as little as $3000 up to $10000. The bottle will need some form of regulator. You will need this just to get the gas out of the bottle so it is not one of those things that can be left out of the system. The regulator or valves that screw into the top of the bottle should have a twin gage on them. One gage that reads the bottle pressure and one that reads the flow pressure, in units of one, out of the bottle. A good flow rate will be in the 2 to 10 psi (pounds per square inch) range. Next you will need some airline tubing to get the gas from the valves into the system.
There are two ways of getting the gas into the system. Either will allow the gas enough contact time with water to get it to dissolve into the water. The first is a bubbling system that is in the form of a small canister inside of the tank. It is hooked by airline tubing to a bubble tumbling chamber. Of those that I have seen, this tumbler will either allow the bubble of carbon dioxide gas to corkscrew up to the top of the chamber of it will follow a set of step like structures. Again both will work but the drawback may be the presence of what could be termed an unsightly thing in my tank. Yes the plants may hide it in time, but the object of this type of unit is to allow you to count the bubbles and hiding it is going to hamper its use. As you will need to test the water for CO2 anyway, the second method I will describe may be better. This method will require the use of a canister filter. By using a tubing connector you should hook up the gas line directly to the base or near the base of the output tube of the canister filter. I would recommend adding a small valve between the gas bottle output and the canister filter hose to further regulate the gas flow. If the output hose on your canister is clear, you can count the bubbles that are released into the system without having some obnoxious looking thing in your tank. The hole(s) of the out flow tube of the canister filter should be pointing at an angle away from the water surface. You should create as little turbulence on the water surface as possible as this will provide the carbon dioxide with an opportunity to exit the water through gas exchange with the air.
Another consideration you may wish to make is the addition of an electronic gas solenoid valve. Hook this and your lights up to an electric timer and you will not have to turn on the lights and the gas every day, it will do it itself. This way you will not over feed your plants when the lights are off which can also severely after the pH of the water.
To test the water, I would recommend the use of a continuous readout mechanism like that made and sold by Dupla®. It is a small and inconspicuous plastic bubble that mounts on the inside of the tank. The device is green when CO2 is good and red when it is not.
Iron food (or fertilizer) can be administered in a couple of ways. One is in a solid soil/clay form that is placed in the gravel and the other is in a free liquid form that is added to the water on a periodic basis. The Clay form should be added only when the tank is set up. Place 2 inches of gravel on the bottom of the tank, then sprinkle the soil/clay additive over the top of this. Next place damp paper towels on top and then add the rest of your gravel, about another 2 inches. This will provide iron through the root systems of the plants. Both Dupla and Tetra® products are available of the laterite soil. The liquid forms can be a bit of a pain as some have a tendency to cloud the water. I have recently been put on to a form that does not. In either case, shopping around and experimenting with some of the forms will help you to find a suitable iron solution.
How does all of this affect plants? Carbon dioxide is a tissue building chemical. During plant respiration, a process also known as photosynthesis, the plant is able to take carbon dioxide from its environment and in the presence of light convert it to a usable carbon tissue and release the oxygen back into the environment.
The equation looks like this:
CO2 (cargon dioxide) + light =
Carbon plant tissue + Oxygen
This is of little interest to the layman but can provide some insight to the goings on in the plant.
Iron is used in the chloroplast cells (the pigments of the tissue) to prevent the bleaching of the tissue. This bleaching is called Chlorosis. It is important that the cells stay a nice green color or whatever special color that each plant may be so that the photosynthetic process is not stopped.
You may wish to add a supplemental amount of trace elements (other chemicals needed in very small amounts) that can be purchased through your local pet store. In some areas your water may or may not contain everything plants need. In most cases it will.
For the layman aquatic horticulturist, the inner workings of the plant provide for little of interest. What may be interesting to know is how the chloroplast cells work. The chloroplast is like a light collecting photoelectric cell. It uses light as a catalyst for the breakdown of carbon dioxide that creates the carbohydrate like substances and is the site of photosynthesis. The carbon/carbohydrate substances are converted into various types of plant tissue which are carried within the system through a network of vein like tubes.
