Water quality and nitrogen cycle

This is what aquaponics is really all about – the nitrogen cycle

Fish poo creates amonia which is eaten by Nitrosomonas sp. Bacteria which then poo out nitrite, which is eaten by Nitrobacter sp. Bacteria which poos out nitrates, which are then eaten by the plants. 

I just took all my levels for the first time in 2 months – (note to self: do this more regularly). 

Everything looks fairly balanced, with only the nitrate and carbonate levels a little on the high side. 

The nitrate levels on the high side could be a good thing, especially seeing as my nitrites are at zero. Seeing as 2 months ago, when  I had no fish or plants, there were no nitrates in the system, I presume this means that my nitrogen cycle is functioning well.  

This also aligns with the recent growth ive noticed with my plants.  This also makes me think that I’m clearly not maximizing the vegetables that this system could handle.  I imagine, that as the plants and roots grow that the nitrates my go down… I’d like to see if that hypothesis pans out. 

The other way it could go is for the fish grow, and the nitrate production potential may therefore outgrow the rate of the vegetable growth to consume it… Which could mean that I have to add more vegetables to balance it out.

It will be interesting to measure this to see how this changes over time. 

Lastly, in regard to the high carbonates, I believe that is a result of a recent top off that I did – and we have very hard water here.  However there is one concern  with this.  Seeing as carbonates are alkaline, yet my pH was last at 7, it does make me wonder if,  prior to adding top up of hard water, the water was fairly acidic. 

Another thing to keep an eye on. 


6 x sprouts in 4 days

Overall, the system seems to have jumped up a gear.  The fish seem well and are feeling strongly.  The plants have taken a torn towards looking better. 

Another good sign, the 6 lettuces I sowed 4 days ago have all sprouted. (although you have to look close to see them all).

With the system more balanced, and with the addition of a fan, I’m hoping these sprouts start off with better stems. 

Last note to self:  to have a more substantial source of  vegetables, I need to figure out a sowing schedule so that I’m constantly growing more plants to replace one’s I hope to one day harvest. 

Time to figure out planting

When  I first planted my plants for the aquaculture it was pretty cold, and it was 4 weeks until i got fish.  

As a result many of my young plants have issues with their stems, and generally doesn’t stay of life strong.   I’m therefore getting rid of the runts (and feeding them to the fish) and resowing a few lettuces. 

The new seeds above are:

3 x laitue verte maraîchère 

3 x laitue rouge Grenobloise 

Planted in floating raft 2, 30th March, water temp 24.1 C. 

Tomatoes for the garden

My Strategy throughout this series of experiments has been to de-risk complete and utter failure by diversifying the range of experiments I’m running.  

I want to get through this season with at least a couple of strong options that I can scale next time around. 

So with that in mind, we re-poted the tomatoes seedlings (all heirloom seedlings that I picked up from Kokopelli.Com.)  

I’m planning to plant these in a raised hugel culture bed in the garden, which I need to get ready ASAP!  

Tilapia feed

I was pruning my sprouts and getting rid of some of the runt sprouts and decided to add it to the fish tank to see what happened. 

I took this “before” photo, which already includes bites out of the leaves with the intention of taking an “after” photo.  

Unfortunately there was no after photo because they decimated the mache sprouts. 

This has motivated me to figure out a way to grow mache sprouts as a high quality feed for the fish.. More to come on that soon.