Global Aquatics was a leader in aquaculture and fish farming technology for over 1/3 of the 20th century, now as aquaculture heads into the 21st. century. Over 40 years of refinement, our aquaculture and aquaponics systems have evolved into the world`s most efficient, state of the art, turn key production machines.
- Business Type:
- Industry Type:
- Agriculture - Aquaculture
- Market Focus:
- Nationally (across the country)
This company also provides solutions for environmental applications.
Please, visit their profile in environmental-expert.com for more info.
We didn't just wake up one morning with a bright idea....
We spent 40 years developing brilliant innovations
Throughout the 1980's the privately owned research and development facility of Global Aquatics, located in Aberdeen, Maryland searched for ways to grow fish in a profitable manner.
Like so many others back in that day, our first approach was to start out with ponds to grow catfish and stripped bass.
After operating our ten acres of ponds for a couple of years we realized this was not going to be a practical solution to solving the worlds need for a new seafood source.
The ponds were too land intensive, labor intensive and with the moderate climate of Maryland we could only grow fish for 1/2 of the year.
By the mid 1980's there were a handful of people around the world who were beginning to experiment with growing fish indoors in tanks. The founder of Global Aquatics was among them.
Like everyone else at the time, we started out with a lot of different tank shapes and designs. Some were large, easy to build round tanks, other were fabricated rectangular tanks of various sizes. The theory being that pretty much all we had to do was to fill the tanks with water, add some fish and 'viola', we would grow the fish... And then the trouble began. It seems that fish poop in the water and it does not remove easily.
What We Learned In Our First Ten Years
One of the first things a fish tank designer must understand is the dilution factor in a fish growing tank. Unfortunately, many do not understand this problem and the results is a fish tank that can not sustain very many fish per gallon of water.
The dilution factor simply means, in a recirculating tank full of water, when new water comes in, a certain amount of this clean water is going to mix with the water that is already in the tank. If the purpose of this new water is to flush out the dirty water and the mixing of the two is too great, then the tank will never clean itself properly. The results, in a fish tank, will be that a lot of the fish waste will not leave the tank but will decay and dissolve right there and pollute the water even more.
A vessel holding water is called a tank. However, just because a vessel holds water does not necessarily make it a good fish rearing habitat nor does it necessarily make it efficient for the operator to manage. Of all the aspects of modern aquaculture that researchers have studied, none has been more over looked than the size and configuration of the very vessel that the growing product has to call home until it is ready for market. We at Global Aquatics have never understood why people pay so little attention to this important part of a system design, especially since we have spent so much time developing what we consider to be the perfect design when efficiency and management are considered.
Small verses Large:
The key to successful operation of any fish system is 'Total Control.' This means control over each and every animal in the tank and control over each and every gallon of water within that tank. Ask yourself these two questions; Why is it that even under the best of conditions a five acre catfish pond can only produce one pound of fish per 400 gallons of water, while even a poorly designed tank system can produce 1/2 pound of fish per 1 gallon of water? Why is it that when there is a total harvest of fish from a pond there is such a wide variation in the sizes of the animals even though they are all the same age and were placed in the pond at the same time? The answer to both of these questions is 'Control', or in the case of the pond, 'Lack' of total control. Now, one more question. What s the difference between a one acre pond and a 20,000 gallon tank? The answer is, 'Some, but not much' What is the difference between a 20,000 gal fish tank and one that holds only 3,000 gallons? The difference is the same as night and day.
It is very important to remember that as a fish farmer you must manage two things at the same time, water quality and the fish. Obviously the less water you have right in front of you in a vessel, the easier it is to manage. There will be more positive water exchange from the inflow and less dilution. Thereby allowing for better water quality.
It also goes without saying that the more accessible the animals are to you the easier they are to manage as well. By managing the animals we are referring to the need to constantly sort the larger faster growing ones from the population at certain intervals during the growth process. This means that every so often the entire population of the tank must be separated into other tanks based on the size of the individual animals. The reason for needing to do this is because as in all animal populations a pecking order occurs whereby the larger, more aggressive animals dominate the rest of the group.
When these dominate animals are removed from the tank and placed with others their same size, a new pecking order will develop within the remaining population. It is because grading a pond is not possible that there is such a variation in growth sizes at harvest time. When grading a tank the faster it is accomplished the less stress is placed on the fish. When you have a large tank containing 25,000 or more animals it may not even be possible to grade this group and if it is attempted it will likely place some of this group under stress for as much as seven times the amount time it would take to grade the group in the smaller tank. Grading the fish is also a requirement for harvesting. Generally in an intensive system the fish are harvested on a continuous basis as they become market ready. Since we know that some of the fish will grow much faster than the others, it is necessary to be able to capture just the ones that are market size from a huge tank of ungraded animals without injuring the smaller that still need more growth time.
Round Vs. Rectangular
It must be remembered why anyone uses round tanks in the first place. A round tank is really just a cylinder holding the water. Because water exerts pressure equally in all directions when placed in a cylinder, round water vessels can be constructed very cheaply using the minimum thickness of materials. The advantages of this fact is, round tanks can be transported to a site and quickly set up. However, this convenience is the only quality of a round tank and this lends no particular advantage where production is concerned. It should be remembered that it is production that pays the bills and the fact that the tanks were easy to install should not be allowed to over shadow future performance. The most obvious first drawback to a round tank is they are space intensive. A round tank in a rectangular room means there is going to be a lot of wasted space in that room in the corners that the tank does not cover. Another draw back is the fact that a round tank has no difference in length or width, therefore water circulation can only occur in a circular motion. Many early designers use to explain that this circular motion was the most effective way to remove solids, because the vortex in the center acted like the vortex in a toilet. They obviously flunked out of physics class because the two vortexes are caused by different dynamic effects. In a toilet the vortex is caused by gravity. This occurs when the valve is flushed there is a sudden opening at the bottom of the bowl. As the water drops through the hole, gravity and the Earth's rotation takes control and causes the water to swirl around the void left by the water that has already escaped through the bottom. This causes a partial vacuum at that point and sucks everything into it. In a round tank the circular motion may resemble a toilet vortex, but instead of being caused by gravity and a partial vacuum, it is being caused by water flow from a pump. This water flow is greater on the outer edge of the tank then in the center, therefore a certain amount of the solid waste in the tank will travel towards the center. However, the problem is, waste deposited along the outer edge of the tank may have to orbit the tank hundreds of times before it finally makes its way to the center.
In the mean time it is being churned and homogenized the entire time and can cause water quality problems as it slowly dissolves. In a rectangular tank the water flow is generally in a straight line from one end to the other. This would mean that a solid deposited in one end of a 25 foot long tank can only travel 25 feet, and in one direction, before it hits the bottom solids trap. In most system designs the time required for the trip may only be a matter of minutes. Therefore the solid is removed in it's entirety before it has a chance to dissolve in the water column and cause water quality problems.
What We did With Our Experience
While experimenting with one tank design after another we were also working with different methods to place the clean water in the tank, the best way to add the oxygen, and design better filters.
One thing we had at the time was a tool no one else in the industry even knew about then. In the late 1950's the founders father had invented a low head oxygen injector to be used in waste water systems. After some modifications to suit our purposes we were able to use this devise to precisely direct the incoming water into the tank and at the same time add the dissolved oxygen the fish needed. Through the use of this injector we cut the dilution rate down to a minimum and kept the incoming end of the tank filled with clean water while it pushed the dirty water ahead of it and out of the tank to the filters.
While this seems simple enough, we ran into one more problem. When used in a tank that was too big, either in length or width, or both, some parts of the tank would build up a turbulence and the water would not move, it just sat there. Unfortunately this happens all too often in most fish tank designs and is difficult to overcome unless things are balanced. After about another year of experimenting with different tank shapes and dimensions we finally figured it out. The maximum tank could be no longer than 24 feet in length, no more than 6 feet wide and 4 feet deep. With the injector working at 12psi and 12 gallons per minute an oscillation is established in the tank that sends the water current flowing back and forth through the tank, from side to side much like a pool ball bounces from rail to rail to get to the other end of the table. This oscillation not only moves the water in a positive manner carrying the waste with it, it sets up numerous vortexes that force the solid waste to the specially designed bottom and out of the fish water column.
With this discovery we now had a true machine. We had a tank with a fine turned water and oxygen injection system.