Backyard Aquaponics
A place to discuss aquaponics

I’m a relative newbie here and as I have confessed before, I have a bias towards the aquaculture system side of things.

My comments are not so much about how holistic you are or what equipment you run. They’re more about the approach… and me just spewing out random thoughts.

As I see it aquaponics is entails running two contradictory systems…

The hydropics side where you want to be meeting ‘at least’ the plants minimum nutrient requirements.

The aquaculture side where you want to maintain the cleanest (i.e. lowest nutrient levels) water you can.

This is where it gets beyond my current knowledge at this stage, but…..

1. What nutrient levels are required by the plants?
2. What nutrient levels are produced by the fish and food wastes?

Obviously answering these would require some monitoring…

On this forum I’ve only heard of the odd addition of iron, so that ‘suggests’ most systems are either neutral or in nutrient surplus. Add to that the good number of people that have had issues with disease in their fish. This again could be suggestive of poor water quality resulting from excess nutrients.

So… if there is a surplus, then there is room to remove some of this surplus, resulting in better water quality for your fish.

If it is then acknowledged that some nutrient removal is warranted, then removal of solids is certainly one of the easier ways to achieve this.

Also note that the removal of solids does not necessary require an expensive (relative to whomever) off the shelf filter. The web is LOADED with DIY solids filters of all types that I believe would be well within the skill range of most here (given the systems you have all put together).

AJ

I've actually been amazed at the reletively low incidence of disease in fish. Considering that many of the people on this forum had relatively little fish experience and the relatively high stocking densities it seems pretty cool to me that disease levels aren't higher.

Just my impression,

Stuart.

Or just feed less. Or keep fewer fish. Even easier!

I'm actually experimenting now to see how much I need to cut back on food to effect a small drop in nitrate levels. It's not an overnight fix like it is for nitrite spikes. Or maybe that's because the nitrate test has wider ranges, and I can't measure a drop of 5 points.

I'm in the "re-cycle everything back into the system" camp. It's a personal challenge! Well, everything except stringy stems. They just clog the pump.

AJ, as Stuart commented, I think there are probably fairly few instances of disease in AP systems, considering some of the stocking densities, and most talk is about adding salt to systems for prevention of disease or treating minor incidences of possible disease. These and practices that would normally happen in an aquaculture system, but unlike many aquaculture systems, most AP people don't treat with anything else other than salt.

Dr Savidov found that AP systems tended to have healthier fish with less disease problems than straight recirc aquaculture systems, due to the ecosystems of micro flora and fauna in the water of AP.

By far the easiest way to remove nutrients from a system is through plant growth, after all, isn't that the whole idea of AP...

So far as exact levels of plants required per fish for extraction of enough nutrients, and provision of enough nutrients, that's what we are discussing... It depends on so many factors, system design and construction, feeding levels, species of fish, planting density, species of plants grown, etc... So, in short... There is no straight answer..

AJ, the nutrients the plants want are relatively benign to fish (although there are limits). These are micronutrients, nitrate, Phosporus, Potassium. The fish waste is ammonia which harms the fish in small qty and nitrites are harmful in small quantities. In Aquaponics, the bacteria are vital that change ammonia to nitrites and nitrites to nitrates. The veggies pull enough nitrates out to keep below the relatively high levels of nitrates the fish can handle. As Earthbound said, the microflora/fauna seem to help fish and plant health. Dr. Savidov raises tilapia and his water looks like pea soup and the fish are very health. Not all fish are that tolerant. The fish in AP are far from stressed and grow much faster than pond raised fish.

Always feel free to express your opinions and ask questions and we always like to hear what you are up to. Welcome

I'm thinking that the majority (if not all) of AP fish illnesses come soon after arrival into the systems ie the fish were either stressed during the move or were sick to begin with. I have not had one fish death or one fish illness from a disease caused by AP at least. Fish with out water don't count!
Gary keep up the great work!

I agree that the diseases normally experienced have been with the fish when they were brought in from the fish farm. My fish had Ich and some had fungus. Dealt with that by using salt and since then have had no issues whatsoever. This is pretty impressive given that the bigger fish I got were riddled with fungus when I got them. I am often suprised to look at my fish these days and see just how healthy they look. Healthy system - healthy fish :-).

Yep, i've kept indoor fish as stupid nitrate levels, just so i can see the cause/effect on them. At circo 300ppm nitrates they didn't want to eat any more. No dieases, just not wanting to eat.

For my part the incidece of disease have been casue by

* diseases carried from supplier
* stress from rapid PH change
*stress from rapid temp change

things like wild ph and temp swings will "stress" fish. This equates to a lowered immune system which equates to disease.

I'd be very surprised if nute levels used in ap (even the higher range) casue fish much stress, but i haven't chatted with my fish for a while..............

We need to do some controlled tests.

i've just planted out winter veggies, so i'll be in it. VB you have a stable and sexy looking system you in for it?

I'd like to maintain NO3 at say 20ppm (does our test kit read that?).

should be real easy to do, just feed more/less

whay ya reckon VB?

Just a reminded that I do have a bias towards the fish side of things. AP is surely a broad enough term to encompass any system that is using hydroponics and aquaponics, in whatever ratio?

With regards to opinions and being able to express them… can I say from my observations this site and its members are some of the best I have come across. Boy’o’boy… jump on to our marine aquarium site, not say something EXACTLY right, or not qualify your every statement, and you get hung drawn and quartered.



Stuart,


I'll take that back. Poor wording and should not have had "good" in there. And based on yours and other comments you guys/girl are right. Upon rethinking, it does seem that most instances are connected to newer systems and/or settling-in periods.

Certainly the number people noting disease is less than any aquarium or aquaculture public forum I've been part of.


Janet,


Absolutely that’s an option that would work in reducing excess nutrients. Though I guess the first thing that comes to mind is, are you then going to achieve the growth rates and stock numbers you want? Leaning more towards fish to match the plants or visa versa?


EB,


Amen to that.

Long story, but I had many people/customers coming toe m for advice on foam fractionator (protein skimmer) design parameters when I ran my business. A classic question was "how big does it have to be". I often got irritable replies when my initial responses was that there was no straight answer and that it 'depends' on sooooo many things. Seems much of AP is just the same, which is what makes it such and exciting challenge!!!

On a different note… there was either an honours or PhD student that did some AP research out at RMIT’s Bundoora campus. I’ve been too busy with my own studies to have a chat with the coordinator to find out what he/she was doing, but form what I have seen the setup is still there. Unfortunately, my studies are leaning more pure aquaculture (amongst other things) or I’d work out away to do research in that area (anyone interested in marine rotifers???).

Sorry digressing….

It does seem that the average AP systems are far more forgiving than the average aquaculture or aquarium systems. Certainly it seems if you consider grow beds to be little more than trickle or wet/dry filters then the filter/stock ratios are very high comparatively.


Doug,


As it is in many of the more advanced marine aquariums and some aquaponics setups.



I guess that gets back to my point though. What is you do have an excess? Assuming you ant to feed at the same rate and stock at the same rate, then you will need to reduce excess nutrient levels somehow.

[quote]The fish in AP are far from stressed and grow much faster than pond raised fish.[quote]

But AP alone does not make for stress free fish! There are numerous factors that could make AP fish stressed and just as many that would see a pond system with less stressed fish. Tis is a whole other topic!!!

Lastly,
I’m a gadget person and see no issue at all with going outside the totally natural system. As I noted earlier, AP must surely be a broad term. Would a 1000L tank and a single silverbeet plant in a hydro-pot still be AP? If not then where’s the line? If mechanical filtration was needed to cover a nutrient imbalance because you want to have a higher stoking density, does it no longer come under the umbrella of AP? I’m not suggesting that’s what anyone meant. Just being dramatic!!!

such a long (but very cool) post



I guess it comes back to being content. If some one is looking for quickest possible growth rates of fish or veggies then i'd recomend running an aquaculture system or a hydro system respectively. Ap functions best in harmony with each component and nature. The further you digress from the natural balance the more human effort it requires. I learnt quickly to use fish suited to my climate! I'll be sticking to silver perch, tandanus cat fish and i'm going to give rainbow trout a go over the winter.

Matching feeding to plant growthrate (via nitrate measurements) might not give the quickest fish growth, but it will be a happy system in balance.

Having said that the fish will tolerate a large variance of nitrates. I'm really keen to get some quantifiable data going on nitrate ppm's as i believe that a system can be run very succesfully on 20ppm nitrate and there is some data on the web about excess nitrates being stored in leafy greens and the subsequent reduction to nitrites after cooking.

Anyway, as you probably know if a system is not in balance then the nitrate will either drop to zero or increase until a water change. Its easy to set and keep them at any level you want by feeding more and then tapering off to the balance point. Ans as easy to reduce but with holding feed until it drops to where you want and then keeping it in balance.

I'm glad to hear our fourum is a happier place than some others

happy Ap'ing

Steve

What exactly are you asking me to do Steve. I am feeding my fish quite a lot, so eventhough I have some good growth these days, nitrate level is still pretty high - over 100. Most of the time it does not seem to be rising though. I don't expect I'll be getting it down to 20, though you never know as the fish eat less over winter - but then again plants are likely to grow less also. At this stage I haven't put in any winter veg - I should start some now from seed.

basically to keep it around 20 ppm and see that the plants still grow fine.

are your nitrates increasing or static at around 100?

if they are static thats good, just means you can drop food for a day here and there and the nitrate will drop and hold at the new level when you re-feed.

Know what i mean?

I'm going to pick up my test kits now (been at steve and anges for a while, and then i'll do it too.

I'd say it would be but if that was all you were doing it would be drawing the bow rather long. Broadly speaking I'd say that any system where you are growing the fish and plants in combination would be AP even if the plant side of it was only watering the plants with fish water. Techincally that wouldn't be hydroponics so may be some would argue that it wasn't AP. I'd inlcuded it on philosophical grounds (mind set of operator) where some may exclude by semantics (in the word science rather than finicky pedantic sense).

As to operating a system with a focus on fish production there are a number of ways to do this. The one that would suit me would be to grow food to feed the fish. A certain proportion of your growbeds could be dedicated to growing plants that go straight into the worm/BSF farm. Nutrient rich water could be diverted into algae culture tanks and used directly as feed or fed to something else which would then in turn be fed to the fish. With a bit of fiddling you could certainly change the balance from whever it was (5:1, 7:1, 10:1 Plants: fish) towards a more balanced ratio.

I could certainly see good reasons for doing this. After all who wants to eat 5 times as many vegies as fish? I'm sure there would be lots of people but not me. Any more plant greater than a 3:1 ratio would have to be incredibly tasty to temp me (any berries that are not straw berries would do it).

Stuart the Carnivore

Steve - the nitrates are a bit up and down - partly due to feeding fluctuation and partly due to evaporation. As the level of water drops in the sump (and therefore whole system) nitrate is more concentrated (until I add water again).

I reckon - though it would be difficult to prove - that the nitrate is actually being lost to the air more readilly at the higher levels. For this reason, I am not sure that a feed or 2 droped would result in the desired result.

man, i'm not taking the piss, but can SOMEONE explain to me how a dissolved salt (nitrate) can be lost to the air???????

please?

It can ohnly be as you mentioned, nitrate conc. goes up with evaporation of water.