An aquarium is a good hobby. But if you want to keep it for long then you need to find an easy way to clean it. I thought of building a fish tank. But knew that the cleaning of the fish tank is ultimately going to be the problem.. So as it was with any other case, I researched to find out the possibility of making my aquarium a self-sustainable one.
As you know there are three type of living agents in a fish tank
1. Consumers (fish),
2. Producers (plants),
3. Composers (shrimps, snails).
If you know how to balance the three in the tank, you got it self-sustainable. On my way..
* I talk to few local experts in the respective fields but all said it is not possible
* Some have done research, and saw them on the internet
* Back yard Aquaponic looks great
* Walstad method is excellent too
So it seems the path ahead is not totally dry..
After much research I started to build it. The end result was a giant tank holding roughly about 3000 liters of fresh water.. The tank was purely built using cement, sand and something called cement brick (native to Sri Lanka I guess). I had three 3 x 2 ft 8mm thick glasses. Later I thought whether I would have added one more glass of same size to improve the inside visibility. But then again less glass mean less sunlight which turn to less algae in the long run. Anyway it is too late to change it now..
The tank was prepared for fish (In theory the new cement layer produce many toxic and also high PH level) by putting water, coconut husk and letting the two stay there for about a week. In a very short period you will see algae grow and then the mosquitos started to breed. In native term, this indicates that the tank is just ready for fish now. The tanks was further prepared ..
• ½ cubic meters of fresh soil – I used fresh soil as that has less iron, and other chemicals. That also can hold fish waist lot longer than soil taken from the surface. This way plant can grow to consume nitrate of water and soil later.
• ¼ cubic meters of large rocks – This adds variety to the tank and also helps to control the temperature inside the tank.
• Aquatic plant, one wheel borrows – They are the oxygen producer and also the nitrate consumer. They help to control the temperature inside the tank. Most of these collected from the paddy field at the end of our land. There are many emergent plants around this area but not many submerged plants. Emergent plants with their aerial advantage can oxygenate the tank bed much faster than submerged plant which depends on the co2 of the water. This area is rich with many varieties of ferns.
• 10 different varieties of submerged plants – I bought many varieties of submerged plants from the local aquarium shops. You need to buy many varieties of submerged plants as you don’t know which can survive under you tank condition. Obviously some of these plants will dies while some other will find their way to establish in this new setup.
Being in an Island I can easily find sea sand.. so I added few basket of sea sand to cover the whole tank bed. This made a 1 inch thicker sand layer on top of the fresh soil.
Then water is introduced to the tank. On my way, I noticed these…
• Mud color in the water
• Sea sand had some chemicals that dissolve in the water and they added a greenly color to the water. From the time I saw that I knew it came to last long. Sea sand is a bad choice, specially the one you can find in hardware shops these days.
I used to live in a village of Sri Lanka and in such places every home has a dug well (dug well water has limited oxygen so that you cannot add fish to this water immediately after you completed adding). The tank is filled with water, mud, and with the dusty color made by Sea sand. About two days later the mud settle down but not the green color added by the sea sand.
So it is time to introduce few fish to the tank. The water channel has enough fish in it. I pick few variety of
1. Dandies (Striped rasbora),
2. Local variety of Fighter Fish (Betta),
3. Two small loola fish (variety of Murrel). I hope to control the fish population with these two,
4. One mada kanaya (Spotted snakehead). It jumps out of the tank twice and then after putting back survived only a day as it does not to have its habitat. The fish needs an ultra-soft mud layer to hide him so died in my fresh soil tank bed.
5. 4 tilapias,
6. few dozens of Weligouva (Bar eyed goby) and
7. Small shrimps to clean the tank bed. But I never saw the shrimp lately saw I wonder whether the fish ate them later. I know some fish eat shrimps.
I went about another 4-5 days. The fish were looking healthy but I never feed them and the water get little clearer now, but still not clear enough to see the fish if they are not close to the glass. I knew that the plants also take time to establish themselves in this new setup. Until that time I have to bear with the bad coloring of the water.
A week pass by, the water got slightly better, mud went away but the dissolved coloring continue to stay.. Some plants gradually started to pick up while some ferns died away. I had a 76 fish in the tank and it was too little for the size of this tank. I decided to add more
1. 40 neon tetras,
2. 20 small white angels,
3. 8 two dotted gouramies,
4. 8 medium size silver sharks (wonder whether it was one of my bad selections),
5. 8 gold barb, and
6. 4 other small fish that their name I didn't remember..
The total added up to 175 fish in the tank now..
About two weeks later, I suddenly noticed that algae is starting to pick up.. It is so evident that algae going to beat the plants. A biological fight has to start now. The plants are still at their very primitive stage, so I cannot wait till they grow enough to absorb nitrate to reduce algae.
The fish pollute water and add ammonia to it. Then the bacteria in the bed of the tank convert it to nitrate which is what encourage the algae growth. As the tank is getting outside sun light during the whole day, I needed to act fast.. I throw few of my trump cards…
1. Covered the top part of the tank with water lettuce (Local variety) to reduce the sun light while introducing a confident nitrate consumer. These are so aggressive that they can beat algae by consuming more nitrate while hurting algae by the way of reducing sun light.
2. Introduced Kang Kung (Water Spinach) that is another aggressive submerged plant and also a vegetable. Kang Kung is so aggressive that start to grow rapidly in days. Now the top part is fully covered and you hardly can see the inside. This is with the mud added with the water lettuce and also the dissolved colored chemicals added with the sea sand.
3. 5 W pump to filter the water – This is a(for Sri Lankans, this consumes 3-5 unit of your electricity and have virtually no impact of the monthly bill) small water pump (600 L/H and I bought it for about 1300/= (~ 13/ $) Sri Lankan rupees) with a homemade sponge filter. I had to clean this every day. I know that once the plants are established I can remove the filter..
The tank start to show some results now. It gets clearer every day.. the coloring added with the sea sand also start to pass away slowly.
Now after about 4 months of operations the tank looks like this