Step 5 - Water and PH

This one cost me dearly. Do yourself a favour an buy a good test kit before you start adding water to your system. You need to test the water BEFORE you add it. I could not figure out why my PH was 8.8 no matter what I did. I lost my 1st batch of 25 Tilapia fingerlings within hours of adding them to the system because of this. They came from a supplier whos water is PH6 and I added them to water which was PH8.8(my test kit does not test higher than this).

So after many hours of research on the net I found out that water has something called a buffering effect, and no amount of PH down or other similar product will change it. You see there are always chemical disolved in the water which you cant see with the naked eye which cause this buffering effect. So everything you do to change it only works for a short time before your water returns to what it was.

These PH flucuations are far more damaging to your fish than a constant high or low PH(within reason). I farm with Tilapia and they can handle PH ranges anything from PH5 to PH11(some sources say even more) as long as it is constant and there are no sudden changes in PH. You can add fish to a system that has a big difference in PH to where they come from, but you have to do it VERY slowly.

That is why it is important to test the water from your supply before you add it to the system. If you find your water is very high or low in ph you could try filtering it through a reverse osmosis filter. We have one of these for our drinking water and although it is slow I was able to keep my fish alive with it. You will need a lot of water so this is not ideal. Larger scale models are available but I found that they are too expensive.

The answer for me turned out to be rain water. Check out this clip on my rain water collector. Aquaponics reqires a lot of water to star up, anything from 100liters to 5000liters depending on your requirements. I needed 300liters for my systems so the rain water was ideal.

Testing the water is crucial in any aquaponics system but for me the 1st test is by far the most important of all.

- Grant

Step 4 - Grow Medium

It is time to choose the stuff you are going to grow your plants in or your grow medium. In aquaponics like hydroponics you need a good grow medium which has the following characteristic:

1. Is stable and does not break down over time.
2. Is readily available in case it needs to be replaced.
3. Provides good support for your plants.
4. Does not leach anything into the water, this is important because you could poison your fish and yourself, or play havoc with you PH.
5. Must be easy to work with.
6. Is affordable, this was number one on my list but I figure not everybody has this requirement so I put it lower down.

I chose 13mm gravel or crushed stone and I have never been sorry except for the very first time I added it to my system. This stuff needs to be washed repeatedly to get all the dirt off it. If like me you are impatient to get going you will not wash enough and you will end up with sediment buildup in your system which could well damage your pump or worse kill your fish. 

I have no idea what this sediment is or what affect it has on your system but I do know it sticks to everything like this photo shows.

The greyish stuff stuck to the PVC pipe is the sediment I am referring to. It sticks to just about anything, you can just imagine what it is going to do to your fishes gills. 

Anyway Backyard Aquaponics has a great magazine which I can recommend to anybody. In Issue 3 (trial by media) they discuss the pros and cons of 4 different grow media. They also have great looking kits for sale if you find yourself in Australia for a day :) 

- Grant

Great websites

Check out this site, they have a lot of PDF files which look pretty good to me.

- Grant