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Overview of Aquaculture

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Overview of Aquaculture

In aquaculture, the roots of the plants are in the fertilizer solution all the time. This is in contrast to hydroponics, where roots are either periodically soaked or a solution is pumped past the roots. I opted for aquaculture as it is cheap and much less care is needed. So much for terminology -- I must warn you that I mix the two terms all the time, so use the one you fancy. The term hydroculture is also used sometimes.

Anyway, hydroponics with pumps and tanks and trays cost money, so I went about doing things with the minimum of resources. If you are on a tight budget, aquaculture is a great alternative to expensive hydroponic schemes.


If you are serious...

If you want to start growing some plants in aquaculture, be sure to start with expendable or redundant plants. Do not try this with precious specimens until you have reduced mortality rates to an acceptable level. Expect one or two to die once in a while. Remember, this is not magic -- the plants are just as vulnerable to problems if neglected.


Vegetable Kits

In Malaysia, aquaculture kits such as the one pictured at left (my first one ever) can be bought cheaply, at around RM20 (USD6) or less. At one time there was this hydroponic vegetable growing fad, and the price of such kits has dropped considerably since the fad had faded somewhat.

In fact, by 2002, the fad has faded so much that it might difficult to find a kit in some parts of Malaysia. You can make one yourself, see the page on the cost of an aquaculture pail.

One slight problem is that the nutrient mix provided is optimized for vegetables, so with cacti you will get mostly plant growth. In the following, I shall discuss some pointers which I picked up through experience, which will be helpful to anyone who wishes to try the same thing at home. Aquaculture, in one form or another, is also practiced by C&S horticulturists who mass-produce plants, but here we shall deal with aquaculture on a small-scale.


The Key to Success

The key to successful cactus and succulent aquaculture is to keep everything clean: plants should be free of dirt, bugs, algae and excess water. This is how it goes: Dirt brings bugs. Bugs attack. Attack leads to stem rot. Stem rot causes fatality. Algae choke roots. Roots die, fouls nutrients. Soaked stem dies, fouls nutrients.

A shoe box painted brown A look inside the shoe box

Almost all of the plants which I put in aquaculture seem to adapt to the conditions, some better than others. You will know if a plant has successfully adapted when growth becomes noticeably fast. Growth can be explosive on plants which offsets.


Stem Rot

While most of my early attempts were quite successful (it's really quite easy), there were a number of occasions when plants succumbed to rot. Eventually I got this problem under control. In order to avoid rot, keep the stem of the plant from getting soaked for long periods of time, and keep the plants clean.

I believe plants will not rot if fungi cannot gain entry past the skin of the plant. Dirty and dusty plants invite mites and other bugs, and once they penetrate the skin of the plant, fungi will have an open channel to attack the plant tissue inside. Rotting is frequently the secondary effect of a bug attack.


Maintenance

Here in urban Kuala Lumpur, I spray my aquaculture plants regularly. With a water hose -- use a stiff spray. In this tropical weather, the stem will dry up quickly anyway. What I want is to wash the plants regularly so that they are always clean. An urban environment is very, very dusty and mites attack very quickly. Keep them clean and they won't liquefy on you.

Every couple of weeks, I clean the whole plant, including the roots. I also clean the cover and the plastic cups. About every month or two, I change the nutrient solution. A key advantage of aquaculture is that you can easily monitor the health of the roots. No soil transplants! No more root mealies!


Nutrients

Plants which I grow in aquaculture seem to be able to withstand a wide range of nutrient concentrations. I have been adding nutrients haphazardly so far (but in the right proportions), and I've not have a bad accident yet. I haven't gotten around getting a pH meter or a conductivity meter, so I haven't kept any proper records of what I put in. Such meters are expensive, and it goes against my policy of minimal resource usage.

Being tuned for vegetative growth, the nutrients will cause a prolonged burst of growth or an explosion of offsets. You can see this for yourself in my other hydroponics pages. See the Nutrients for Aquaculture Page for information on the nutrient solutions I use.


Potting Medium

The stuff used in the cups to hold the plants in place is a mass of cotton thread. I use it simply because it comes with the vegetable kit, and one can get the same thing by cutting up rags. A problem with this potting medium is that sometimes there will be an algae problem.

In addition, if a part of the cotton is soaking up the nutrient solution, salt depositions and algae are likely to form in a hot tropical weather due to evaporation. I've looked into alternative growing medium, but a wad of cotton thread is easy to handle and wrap around plants. You don't have gravel spilling all over the place. I got some rockwool, but I don't quite trust the coarse texture. I'm afraid that it might break the skin of the plant and introduce an infection.

If the plant is large, the cup and the medium may be hidden. Make sure you check all the nooks and crannies regularly, for bug might pick those spots to wreak havoc to your plants. A perfectly good plant can liquefy on you suddenly if bugs get into places where you can't see them. Every few months, I take each plant out in their cup and give them a good stiff spray of water. This dislodges the salt deposits and removes bugs.

Alternatively, if you make your own cover from styrofoam, you can customize hole sizes so that the plant just fits the hole. Holes can be made with a hot soldering iron (actually, a joss stick is better) -- it might be a bit messy, so get a cheap iron for this purpose.


Root Problems

Some succulents have fleshy roots. This is not good as such roots have a real nasty propensity to rot. Whole sections, or almost everything, can turn brown and drop off. However, if you can keep the roots healthy for a while, growth can be spectacular. If the roots turn brown, they are being choked due to lack of oxygen. When roots are choking, remove them and let the roots grow back. Alternatively, see the next section on using air pumps.

I have a couple of Gymnocalycium quehlianum with long taproots, with a good part of the thick trunk in water, and they seem to be doing well. So far, anyway. Soaking root sections is not always fatal.

The best kind of root structure is the tree-like kind. Myrtillocactus geometrizans has such a root structure. The roots don't bunch together as much and the plant is very strong and have never rot in my aquaculture boxes.

Plants which produce only a mass of fine roots need monitoring from time to time, as a huge mass of fine roots will choke each other in a stagnant solution. If you put some of those rooting hormone, things might go out of hand. After a few weeks in a stagnant nutrient solution, the whole ball of root will rot. Ooh, and that smells really bad...


Using An Air Pump

If you intend to use an air pump in an aquaculture box, note that the oxygen content of the solution will change. I noticed that in an oxygen-poor solution, a big mass of fine roots are produced. If the water is never changed, these roots will eventually choke.

With an air pump, less roots are produced, and these roots are thicker. So if you are adding an air pump, it might be more convenient to start with rootless plants, so that proper roots can be produced for appropriate conditions.

One thing to be aware of when using an air pump is to ensure that you do not bubble the air near a stem that is prone to rotting. This is because when the bubbles burst, tiny droplets of water is sprayed out. If a stem is nearby, it will be continually soaked, so it may rot.

An air pump is much cheaper than a solution pump. Most aquarium air pumps runs at about 2W to 5W, so electricity consumption is almost negligible. Your phantom electrical loads are probably much more than that.


Summary

Here is a summary of what I do for cheap aquaculture:

Here is a summary of my maintenance tasks:

For more on my attempts at aquaculture, please see my other pages on this subject, showing the things I've done in the past few years.


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  Last modified: 2002-08-26  Copyright © 1997-2002.  Kein-Hong Man.  all rights reserved