Backyard Aquaponics
A place to discuss aquaponics

Hello folks!
im new here and I would like to know if anyone has ever tried this calculator:
http://www.aquaponic.com.au/calculators.htm

It seems to be very complex in its calculations and the author provided a 14 page guide for it too.
I noticed it differs from some of the 'rule of thumb' we see around...

I think I will try it, I have a 1,44m² grow media area, at@ 300mm.
I will use a 500L tank (will fill only 370L).
According to this calculator I should have 5,3KG of fish and feed them @1,5% of their total weight once they grown and more when they are small.
According to the calculator and I should flood and drain at least 84L per hour.
not even sure if this is correct, it will be my first system...

So did it work for your system?
Any thoughts?


Thank you!

Dr Wilson Lennard is exceptionally knowledgeable on subject aquaponics, however, unfortunately some of the tools he (and many others) have compiled only look at single aspects of aquaponics designs at one time, not the holistic system design. You might have to use many different tools from Dr Lennard and others, revisiting them many times before finalising your design.

For example: if you have 370L of water in your FT and using a pump which is delivering 84L per hour to the GB in a CF system, you're going to have to be using very small diameter pipes to be able to keep the water moving fast enough to deliver solids to the GB for mineralization, but then the pipes will be so small they would simply clog with the waste they are supposed to be moving! Let's assume water velocity 0.1m/s, Q = 84l/h = 0.084m3/h = 0.000023333l/s

A = Q/v = 0.00023333m2 equates to a pipe with inner diameter of 8mm, which is tiny!

Even if the pump and piping were slightly bigger and employed in a timed F&D, the waste would probably be only deposited at the inlet to the GB and not evenly spread across the surface area of the GB which one of the factors to successful mineralization of waste in the media beds.

The next thing to consider, if you're only going to be "trickling" water around the system then you're going to need additional aeration, so you'll need to factor in the costs to purchase in operate an air pump; if you move more water through larger piping into a larger bed (to move water sedately through the media) you may not need to run an air pump continuously (have it on standby as a backup). So, even if you could move the solids into the GB for mineralization, you might still up wasting money or killing fish due to other deficiencies in the system design.

Have a look at all aspects of the system design, don't focus on only one component. It is a circular process, so start working within the limitations you already know, whether that be a space limitation, cost limitation, components already owned etc and work around the entire system.

On feed rates: see if your feed manufacturer has recommended rates; they can be quite surprising and may influence the design of your system as the feed loading changes throughout the life of the fish.

@bunson thank you for your reply! Im glad I stopped by to ask before I started anything.
I will do some more reading and start to compile a list of thing I need to address just like you suggested.

Gratitude.

In the interests of fairness and my bottom lip someone needs to yell at Bunson for including calculations in his first reply to a new forum member.

@Kreo: What he said.

In all honesty, don't over think this. Pretty much all you need is a body of water, a pump, and some grow beds. Of course you don't want 50k gallons of water with one grow bed, but if it looks even to you, it will probably work. I never calculate anything, and my system is running great. Just build something that looks right, and have fun.

With reason Helomech's advice is not a bad idea especially if you just copy someone else's design that works and has been working for a few years.

Also its a pretty small system. I'd just have a GB twice the volume of the FT and a sump big enough to hold enough water in the GB and keep the pump appropriately submerged.

Thanks guys!

About the sump... I dont want to use one!
Since I have limited space I would like to maximize the use of it at least for now... I saw some systems in which the grow beds drain directly into the FT, some people said it help with oxygenating the water. but if I use this model (without the sump) I cant have my grow bed with the 2:1 ratio or my fish will suffer, got me thinking... maybe go with 1:1?

Thanks again for taking the time to help a noob! my goal is to perfect this technique and soon enough(few years ;p) distribute free quality food.

I do not use a sump. Just need to have more fix tank volume so the fluctuations are not a issue. I have 625 gallon tank with 6 IBC grow beds. I really can not even notice the tank fluctuating.

I used Wilson Lennard's calculator when designing my system, and it has been working very well for me. If you are looking at a very small or very large system, or very high or low stocking rates, it probably wont apply very well.
I certainly found his water pumping rates a better guideline than the oft repeated "turn over the FT volume every hour", for my system.

If your GB is 1.44m2 at depth 300mm this is about 430L
Filled with something like hydroton media will take about 40% to flood, 173L
Your FT has 500L capacity but you only want it filled with 370L of water, then each time you flood your GB you are going to be taking about half the water out of the FT! Depending on the shape of the FT, this may be too much of a reduction??

Can you completely fill all 500L of the FT, so that when the GB is flooded, it's only using about 1/3 of the water?

Have you considered a CF (constant flow, constant flooded) design?

+1