Backyard Aquaponics
A place to discuss aquaponics

GREAT job on the towers/painting, JoC!

I would probably say get a second 2000 ltr/hr pump. Plumb it so that one of those pumps runs just the towers and the other runs the fish tank/grow beds. Then you have more flow overall and your two pumps are interchangeable.
I would get an additional air pump anyway so It could run on battery backup in case of emergency.
That is just me living in a sub tropical swamp where keeping water aerated enough is a challenge through the warmer parts of the year.
Drawback there is you would be running a little more electricity. You might do some extra searching to find the most economical pump to run for the amount of flow you need at the 2 meter head (simply going to the 3000 l/hr pump might not be your best option since a different pump might give you a very different flow rate at the higher head so some extra shopping around looking at pump curves and power use could help.)
Keep in mind if you decide you need to stop the flow to the towers say during cold spells or something, it would mean re-balancing all your flows if you are using a single pump but if you have a separate pump for just the towers you could even set that on a timer for certain seasons or leave it run constantly during other seasons without messing up the flows to the rest of the system.

The garlic hot pepper spray works well for me in my dirt garden, also diatomaceous earth. I read an article a few years back that basically said that plant pests carry their own disease antigens inside them, and if you can gather as many of them as you can and whiz them up in a blender dilute in water, strain and spray back on plants, it kills pests.
Hay worth a try, hope this helps.

Oh, wow I can't believe I missed this sticky. I'll just start linking this for now on when it comes to sizing/stock questions. This is especially true when it comes to stocking density. I see a lot of people suggesting either number of fish or absurdly high densities for a beginner/hobby system. The former is misleading because not everyone stocks tilapia or for that matter harvest at the same time. In the later you can run into some serious solids filtration and water quality issues if you don't tend to mucking out your beds and pipes or adding supplementary mechanical filters. At what stocking density this happens is up to debate. But I'm rather partial to the idea of taking it slow.

I kinda feel like the 2:1 ratio for GB/FT is a little on the high side in some instances but you can never have too much filtration and more water in the system dilutes the nutrients/toxins a bit more. Not that media beds take that much water but every bit helps especially at higher densities.

Personally I'm going to probably go with 15-20 Kg/1000L to start. 30 Kg/1000L seems like a reasonable max from what I've read.

I don't feel that the 2:1 Grow bed to fish tank ratio is too much grow bed at all, especially for anyone who is at all likely to even approach the max stocking density for the fish tank. Of course to have the 2:1 ratio you have to build a system that can cope with water level fluctuations so most simple systems are more like 1:1 and the key here is you have to stick with only stocking as many fish as your filtration can support.

And I know of people who have run more like 3 or 4 times the amount of grow bed volume as fish tank volume.
In fact I have a system that is currently running a 1000 gallon fish tank and I have about 3000 gallons of media beds on that. I stock the 1000 gallon tanks usually with only about 100 advanced fingerlings, granted, they are channel catfish and I do tend to grow them big. That system is full of indexing valves so the water level fluctuations are small enough to be dealt with in a 300 gallon sump tank.

What I normally tell people (ok this will be in gallons/cubic feet and lb since I don't think in metric and neither do most of the people I'm helping) for hobby/backyard systems is start out stocking no more than 1 fish (if it's max weight is expected to only be up to 1 lb) per cubic foot of media bed and have a minimum of 5 gallons of fish tank water per fish. If you expect to grow fish bigger than 1 lb, double the grow bed and fish tank volumes for each fish. Then once you are more experienced, you can adjust your stocking appropriately but if you have to ask how many fish you can have or how many you need, the answer is always LESS.

I think the standard BYAP recommendation is up to 25 fish per BYAP grow bed assuming you plan to harvest fish at around 500 grams.

Remember these numbers are really to get you started right, we have seen so many people put the MAX fish in before they know anything about what they are doing and killing all the fish before they even hook up the first grow bed because they were under the impression that the fish had to build up the ammonia before they could set up the filtration.
ANYWAY, it really doesn't take that many fish to grow a lot of veggies and it can take lots of grow bed to handle large feed/solids loads.

Well as far as the 2:1 I was inferring at low stocking densities. Also keep in mind that media can get quite pricey depending on what you use. There is also sometimes the matter of space or even weight. If someone was building a small system on a balcony or a rooftop being mindful of the dead/mechanical loads the structure was initially designed for. So, I just meant it's not something to be completely inflexible about. As you said some people do 1:1 just fine and others do even higher. Case by case.

I certainly think that total system water volume is often overlooked in the discussions here. I mean that at any given stocking density and feed rate that the resulting water soluble substances are then mixed and slowly spread out over the total system volume. At higher stocking densities this helps you buffer spikes to some degree. At lower densities diluting your nutrients too much could mean problems for your plants (especially with NFT where the volume of water the plant roots are subjected to are by design lower). Now granted this is probably only an issue at the extremes. And that's not to say that these rules of thumb don't address this indirectly.

At the end of the day a system isn't simply a sum of it's components that fit into a neat little generic formula. Once a system is running it's a matter of making sure all three organisms are healthy. So many variables affect that. Fish species, density - not just of fish but also plants, type of crops, etc. Everyone is healthy and water quality is good? You're golden. In your example of 3:1 I bet you have no problems with mineralization and rarely have to supplement. The fact that it's indexed means you don't have to dilute your system with a huge ST so mg/lit.. err ppm stays at reasonable levels.

Lol the units thing is hard at times. In practice it's much easier to visualize things in the units your accustomed to using. I only tend to size things in metric because I've yet to build my system. Which means my opinion means nothing, NOTHING I SAY. Seriously I realize I'm a greenhorn. But until I build my system all I can do is have discussions like this

Less is more and thumbs are for starting lines?

So around 12.5 Kg/1000 Litres or 27.5 Lbs / 264 Gallons. Err.. wait you said per GB. Nvm. I assume you're talking in terms of IBC GB @ 30cm.

Yup, fishless cycling is certainly important.

One thing I read in one of Wilson Lennard's fact sheets made sense to me. Without additional mechanical filtration there is a point where media bed mineralization cannot keep up with solid waste that is entering the beds at a fixed point. By virtue of solid waste being solid it doesn't tend to spread out much from the inlet pipe to a bed. So while in theory a bed has a lot of volume in which to support the breakdown of solid wastes it only occurs in a smaller portion of it. I only mention this because you mentioned needing large GB area to handle large feed/solids. GB's are certainly enough filtration for most.

Uh, no the BYAP grow beds are not an ibc top at 30 cm. They are closer to twice that footprint.


If you have water flowing constantly into a single fixed point in a grow bed, then, if you have much feeding going on, yes you are likely to see that point have some problems with "fish poo pavement" or needing to "poke it with a stick" frequently. I have seen far less of that problem with the Timed flood and drain beds being fed at a single point. I do have a small system (kinda backyard scale) where the two grow beds get water just in one corner and they flood and drain via bell siphon and the corner where the water flows in does slime up and then algae grows and the water over the surface spreads and I have to go clean off the algae matt and stir the gravel regularly. But I must admit, I'm making that system work pretty hard as it is definitely overstocked according to these rules of thumb.

Anyway, BYAP generally uses distrobution grids over their grow beds so that the water isn't entering the bed just at one point. I've personally only used grids in locations where the water flow through the gravel isn't fast enough for my sometimes overly rabid filling of some rather narrow grow beds.

Ah, you did say BYAP I missed that detail. At any rate it looks like that rule of thumb was about the resulting nutrient output needed for a fully stocked GB. That makes more sense to me then say a ratio that sizes GB w/o consideration to the stocking density used.



Good to get some confirmation that it can be a problem in certain cases. What is it about the timed flood and drain that keeps them cleaner? Are the solids settling in the ST? Sorry I just got back from the movies and it's 2am here so maybe I'm missing the obvious.



Yes, I read about the inlet manifolds too. I didn't bring them up because I figured it would be shot down as completely unnecessary. Which they can be. Just another tool to be used when and if you need it. Overly narrow? Wouldn't that fill up faster? Or are they overly long as well? Again maybe I'm missing the point. Zzzzz.

I think the point where water runs in getting a chance to dry out just the littlest bit allows the solids to break down more and spread into the bed. And I don't think it's the solids themselves per say that cause the real problem but actually the bio-slime and algae build up that happens in a situation where it constantly has water flowing.



I have three beds that are 1 foot deep by 1 foot wide and 21 feet long. I found that if I dump the water in just at one end while the drain is at the far end, even when there was nothing but gravel in the beds, the end where the water was flowing in would overflow. Again these are beds where it is timed flood and drain and I'm dumping the water in quickly so that I can flood the bed in under ten minutes. I found I needed to distribute the water down the whole length of the bed since the flow through 1/2 inch gravel wasn't fast enough for my taste and once roots are taking up space the flow would slow more.

Hmmm, here's hoping evap keeps the surface area ideal for algae down for me. Not that I should really be hoping for more evap in the desert Or perhaps I could have two or more inlets per bed and cycle thru them to both spread the solids and keep from having an area that's always wet. That sounds overkill to avoid a little algae tho. lol.



Ah, yes, that makes sense. It's like a narrow DWC with the impediment of the media. A DWC filled with molasses. Pretty long retention time.

Here comes a point where something no longer becomes a "rule of thumb." Is there more to it than just a 2:1 rato? Sure, but the 2:1 rato makes a good rule of thumb. People have to start somewhere.

+1

Well said Ron, when people ask the question they want an answer and "how long is a piece of string?"
is not answer or what they want too hear.

Rule of thumb is a great starting point, any answer either side of that would be the wrong advise.

Yep too true.

I've had people get MAD at me when I couldn't give them a definitive short sentence answer to the question, "How long does it take the plants to grow?" They got MAD when I asked them what kind of plants. So yes how long is a piece of string? and How long does it take hair to grow?

Gotta start somewhere.

TCLynx your very first post when you started this thread is some of the best advise you can give people starting out in aquaponics and I take my hat to you for the thread and it's information, that advise and the advise found in the IBC of Aquaponics is very helpful for anyone starting out.

I personally used your advice when I first started out along with the advise of many others on this forum and could not have got anywhere without it.


If you don't have the correct starting point it's a very hard road ahead.

Generally speaking its just not relevant. A system with a larger volume will develop nutrient concentration levels similar to a smaller volume system it just takes a bit longer to get to equilibrium. In the long run it generally makes no difference.