Backyard Aquaponics
A place to discuss aquaponics

Yep, removing water is the best way, if you dont have any plants and don't want to bother with anaerobic denitrification procedures.
I have 6 gravel GBs now planted out to use up the NO3, and 900+m^3 of surface area, so I guess I'll find out soon enough if ~2kg of food per day is doable, assuming I can keep the water cool enough by then.

Thanks all, this has really helped me clear up some of the RAS questions I had.

Martin.

And so also for me...

Clearly there are some conflicting issues..

There is an opinion that NITRATES at reasonable levels are fine and even at levels like 150 is fine..

I became confused when I saw a uTube video from a most prominent source, where they described a semi closed RAS that omitted to talk about Nitrates.. the assumption was that they used water change to reduce levels...

So logic is correct and unless you are prepared to swap water out to the GROW system, then you WILL need to cater for rising nitrate levels even in small systems..
I had considered finding a tree type plant that could help with reducing nitrates.. ideally, something that was potentially productive, and which could handle fish management procedures like salting ..

Any suggestions. ... eg fruit tree that is 4part salt tolerant... (emergency only)
My tomatoe tree would be good, but likely short lived..

This has come full circle to my first obtuse question of what typical media per fish was recommended for a "solids-less" RAS.. and I omitted to describe how the media would work with nutrient sucking sacrificial plant/plants..
..
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I thought this was a RAS system?

Now it is a AP system where you are removing solids?

That highlights the issue.. Can you run a RAS long term and ignore nitrates, or does - RAS imply water change..
I would prefer not wasting water

And yes, i was considering a partial RAS-AP, where a hardy nitrogen loving plant will chew up the nitrates ..
Only likely problem.. I doubt there is such a plant that will thrive with not other supplementation and medium salt..
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You cant really run a RAS and ever ignore any part of it.

You can run a RAS without water changes (or at least not many) but to avoid the water changes requires installing de-nitrification components and they require a fair bit of extra energy to run.

That is the brilliance of integrating AQ and HP. The parent production methods can reduce their water use to almost nil but only by installing expensive kit. Expensive to buy and expensive to run. Aquaponics on the other hand achieves exactly the same water savings and you actually get to reduce the energy use rather than increase it.

Chard, cabbage, celery, spring onions and other similar plants will certainly use up Nitrates and grow well in 2 or 3ppt salinity, that's what I'm using, amongst other things, to soak up some of the N in my system, currently at 1.04ppt salt.