Aquaponic System Components

Round Tanks
Tank Drain System
Waste Removal
Biological-Filter
Aeration
Grow Bed Medium

Fish Tanks
Depending on whether it is for commercial or backyard purposes, the size and shape of the fish tank or grow pond is basically up to you.  You may consider either a rectangle or round tank taking into consideration the size and shape of the space you have available or in the case of a backyard project, you can design it to be decorative as well as functional and design the shape yourself for decorative effect.

RECTANGULAR TANKS

Rectangular tanks utilize available space better than round or odd shaped tanks and can be built using a number of different ways and you are only limited only by your imagination.  Regardless of which design you choose, it is suggested that some measure be taken to raise the sides steeply to a sufficient height to keep out aquatic intruders, mainly frogs, but snakes are not unheard of especially if the frogs are present.

• Inside a greenhouse most anywhere or outside in warmer climates, an excavation can be dug in the earth with one end slightly deeper than the other to aid in the collection of waste and lined with a heavy mil greenhouse black vinyl.  The earth removed from the desired area can be banked up around the top edge of the excavation.  when the vinyl liner is put into place, there should be a sufficient amount of excess to lap over the top of said perimeter of dirt.  The added dirt around the edge will also help increase the depth of the tank..
  
  When filling the tank, do so slowly making sure to gently pull out as many of the wrinkles from the vinyl as you are able to do to make the bottom and sides as smooth as possible.  You can carefully fold the vinyl at the corners making a neat corner and the water pressure will hold them in place.
  
  After the tank is filled, the top sides of the vinyl may be pulled over the banked earth.  You can then place more earth on the outer edge of the vinyl to hold it down securely and decorate the edge with stone.
  
  One other method would be to build up the sides with landscaping timbers which you can purchase at most home improvement stores.  A height of about 2 or 3 feet is usually sufficient to keep out the frogs, but don't forget, it you tank is outside are not secure, Raccoons will be more than happy to raid your installation nightly for a tasty fish dinner. 
  
  After you have reached your desired height, you can then wrap the plastic over the top and fold it under 3 or 4 times and using small squares of rubber cut from an bicycle inner tube, place nails about every 3 to 4 inches apart all the way around the top.  You then add one final layer of timbers over the plastic to give it extra security.  This final layer will also act as an overflow preventer if the tank is exposed to rain etc.
   
• A more elaborate method, though longer lasting is pouring a concrete pad and building the walls using concrete blocks.  Once completed, the tank will have to be flushed thoroughly and painted with a non-toxic swimming pool paint to seal it.
   
• Tanks can also be built using thick plywood and 2X4 framing.  All areas where the plywood intersects should be sealed with a generous application of silicone sealant and the entire interior of the plywood tank should be painted with a non-toxic swimming pool paint to prevent rot.
  
  A list of construction methods could go on forever as you are only limited by your imagination.

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ROUND TANKS

Round tanks can be made from either Polyethylene or corrugated steel tank rings normally used for watering tanks for horses and cattle.  You can also purchase pre-built steel stock watering tanks that have the bottom already built in, but they present a problem in transportation as they are not collapsible. The corrugated steel tanks can be used with a vinyl liner placed inside the steel frame. The steel rings will give a quicker solution to the construction of a tank, but being round, does not utilize available space economically.

Corrugated tanks come in sizes from 9' to 30' in diameter with side walls of 3' to 6' high. The vinyl liner should be handled very carefully when placing it inside the metal rings as there are often sharp edges which can cause minute holes in the liner which will haunt you until the end of time with unexplained water loss.

For those instances such as hobbyists, schools, and small commercial growers, corrugate steel tanks and Polyethylene tanks are a quick, economical way of constructing a tank and getting the show on the road.  Both come in a number of sizes as mentioned earlier for the steel tanks and as for Polyethylene tanks, the most common sizes are the 300, 500, 800, and 1200 gallon tanks and both may normally be found at Tractor Supply Corp.

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TANK DRAIN SYSTEM

A drain system should be placed in the bottom of the tank to pull the water primarily from the lowest point of the tank or where tank design designates waste collection to be concentrated most. The water then moves to the Sump Tank for waste collection.  The drain may be installed using PVC connections through extra added layers of rubber or vinyl and sealed with a generous application of silicone sealant.

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WASTE REMOVAL

Solid waste comes in the form of fish excrement, uneaten food, trash/dust particles blown in, and other unknowns which come from "somewhere".  Physical removal of said waste should be done on a schedule so as to not allow it to build up too much as it can be responsible for 70% of the nitrogen load in a system.

Solid waste causes heterotrophic bacterial growth which in turn produces additional ammonia in the system.  A sump tank configuration is a great way to make collection of said waste much easier.  As seen in the graphic HERE, the flow of water hits a baffle that slows the flow of water, thereby creating a "dead spot" in the water flow, which in turn enables the waste to settle to the bottom of the sump tank at a very efficient rate.  The Sump Tank configuration is simple to use and easy to clean.

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BIO-FILTRATION

A bio-filter converts harmful ammonia to non-toxic Nitrate and can also aerate the water assisting in the removal of harmful gases from the water.  Bio-filters utilize two types of bacteria, Nitrosomonas and Nitrobacter to rid the water of the nitrogen produced by the fish and broken down waste. The Nitrosomonas bacteria converts the ammonia (NH3-N) in the water to nitrite (N02-N) and the Nitrobacter bacteria then converts the nitrites to nitrates (N03-N) which are not toxic to the fish.  Nitrates are a very high quality nitrogen source which is where the plants come into play in an aquaponics system by removing the Nitrate from the water, then the cleaned water is returned to the fish to complete the cycle.  It is essential to monitor the ammonia and nitrite levels in your system on a regular basis.

An established bio-filter, working efficiently, also produces several acids; carbonic, nitrous, and nitric acids as by-products of their process. This condition will drive the pH of the water down and it therefore becomes important to also monitor the pH numerous times per day and adjust it according to the desired pH for your system. 

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AERATION

In addition to the aeration provided by the bio-filter, additional aeration of the water must also be provide in some manner to assist in removal of harmful gases which build up in the water during the filtration process.  This can be accomplished in a number of ways according to the volume of water involved.  The construction of an aeration system is discussed HERE but may be as simple as placing aeration stones in the tank which are attached to an appropriate sized air pump.

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GROW BED MEDIUM

Your choice of a growing medium will depend on what plants you intend growing and the type of system you have set up. You should choose carefully and always make sure your grow bed medium has never come into contact with herbicides, insecticides, petroleum or any chemicals of any kind.

One medium that is a good choice is washed river gravel which is nice with its well rounded edges that are easy on both hands and plant stems.  Get it at a size of about 1/3 inch to 3/4 inch in diameter. Pea gravel is another good choice, but don't forget that gravel that is too small in diameter can clog very easily and will retard or halt water movement all together.  Coconut husk is also great in that it is also bio-degradable when changed out.  It is also possible that you will not be using a growing medium as in a free flow system.

Regardless of what type of medium you use, always make sure to rinse it thoroughly before placing it into your grow beds.  Most stone and gravels and even coconut husks contain dust and sand and other small particles that could cause you a problem down the road.

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