Managing Nutrients in Prawn Farms

This post is not going to be me going through the ins-and-outs of prawn farming and the best ways to manage water in a prawn farm.  The simple reason is because I am not well versed in prawn farm management.  We all have our limitations…. also don’t ask me to ride a motorbike, because that wouldn’t be pretty either.

But I do still want to write a post about prawns and prawn farming, because I do know that management of nutrients in prawn farms is so important.  There have been a range of trials done in the past, one particular report from a few years back is very interesting. The report looks at research on how to reduce nutrient levels and improve farm effluent, and that includes the use of bivalves, and other species such as mullet and rabbitfish.  I don’t know what a rabbitfish is but I am going to Google it later!

I also found another interesting report by a department of the Queensland Govt on a different methods, and these ranged from duckweed ponds through to Polychaete sand filter beds.  It is worth the read, but don’t head over there until you have finished here, as I want to give you another point of view and something else to think about.

Prawn farm ponds with a green colour from the algae growing in there

Prawn farm ponds with a green colour from the algae growing in there.

These reports look at different ways to manage the nutrients and the algae in your ponds.  This is really where this post is heading. Because there is, undeniably, a need to manage nutrients.  These reports I mentioned above offer options and ideas.

I can’t leap in here with the solution because I am not ‘Mr Prawn Expert’, but this is a conversation I would like to have.  If you have looked at other posts on this site, or looked at the product info, then you will know that I reckon Diatomix is a sensible path forward to managing nutrients.  If you arrived directly to this blog post, then I recommend to you that you have a look at what Diatomix can do.

The main drive behind the methods to manage nutrients in prawn farm ponds is to move the nutrients into the biosphere and out of the water, where they are soluble N and P.  Algae are recognised as one of the quickest and fastest ways to do this.  But actually ‘managing’ or ‘controlling’ the algal cultures has not previously been on the table as an option.  Now it is!  Now you can add Diatomix and get the micro-nutrients that all algae need to be absorbed by only one class of algae.  Only the diatoms will absorb Diatomix, so only diatoms will get the boost of micro-nutrients and then start growing and out-competing the other algae.  When that first bloom of diatoms backs off, you can encourage more diatoms with another dose of Diatomix.

With more diatoms in the water, you are making more food, and better food, for prawns, and for zooplankton, which are also food for prawns.  Also, with more diatoms growing in your wastewater management  ponds, you are reducing the soluble N and P so you can release water sooner, with lower nutrient levels, higher DO levels and better pH levels.  All important management steps.  You will also have reduced the volumes of water you need to store to manage the nutrients as nutrient absorption can happen pretty quickly with diatom blooms.  So I anticipate that more ponds can be used productively, and fewer ponds are used for wastewater.

But this is still me applying my knowledge of algae and diatoms, and of Diatomix, but not giving you any hard facts and figures.  The only reason for this is because right now, in March 2015, Diatomix is new to Australia and I haven’t trialed this in a prawn farm yet.  I hope to change that very soon, and when I do, I will post about what happened.  In the meantime, if you want to know how this story ends, or how it proceeds, then we can trial it together and find out.  The world loves early adopters, pioneers and innovators.

If you want to see what else is out there, you have now read about what I think is the next best thing out there, and I believe it will be good enough to solve the problem, and stop the endless search.  Let me know if you want to give it a go.



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