Add nutes until mature?

[Daniel Gunloche]

Hello all,

I am in the process of converting my Hydroponic system to AP.  I am planning on cycling the AP system separately (fishless) for a while.  But I understand it will still take over a year for the AP system to mature to full effectiveness.  Why have I never heard of anyone taking TDS readings and simply supplementing the system with organic hydro nutes to maintain the desired TDS readings?  I would think it would not be harmful to the fish if the system will eventually get to that level in a year or so anyway.  And could organic nutes be added to a mature system every year to raise the TDS in winter for tomato production?  Is there a maximum TDS level that the fish can handle? And if so, what would it be?  And would it be taboo to add small amounts of chemical hydro nutes to an AP system until it matures?

Thanks

Dan

[LogicalHydro]

I am honestly working with the same question and just started a little project myself that relates to a point: http://aquaponicscommunity.com/forum/topics/organic-nutrient-challe...

 

I am having problems relating PPM of aquaponic water to organic nutrients and what the difference is and how they relate. So far I have heard this and that about endangering fish and algae problems with organic nutrients. What kinf were you thinking of using?

[LogicalHydro]

I would never suggest chemical nutes though

[TCLynx]

TDS readings are really just a measure of the conductivity of the water estimating the strength of the nutrients based on the normal mixes of mineral salts usually used of aquaponic nutrients.  I've found that TDS readings are not going to be of much use in getting the right "nutrient" levels for plants in an aquaponic system and if you ever have to use any salt to treat fish it will spike the TDS reading way off the chart while not actually providing the right nutrients for the plants.

 

It is not necessary to have a TDS reading in order to grow tomatoes.  My system usually runs a TDS reading that according to the Hydroponics books isn't even strong enough to grow lettuce let alone tomatoes but I grow lots of tomatoes and bananas, and other greedy plants with a reading down around 2-3.

 

Also, using hydroponic nutrient mixes in an aquaponic system is not necessarily safe for the fish.  In Hydroponics you change out all the nutrient every so often since the levels get out of balance and need to be dumped and replaced.  In aquaponics you really can't do complete dump and replace of all the water as that would be really stressful to the fish and bacteria so if you are constantly adding chemical fertilizers like for hydroponics you are likely to build up certain lesser used nutrients to toxic levels.

 

[Daniel Gunloche]

Right now I am on chemical nutes, have not looked into the organics yet.

[LogicalHydro]

TC,

 

I agree with everything you say and I'm glad you have the experience to share with us. Is there any other way to monitor beneficial nutrients besides nitrate PPM readings?

 

Also a lot of hydro mixes change pH levels a lot without adding buffers and it wiill most likely be devestating to fish or plants, or both.

[LogicalHydro]

Daniel,

 

Which line of nutes do you use?

 

I have found some seemingly very beneficial organic nutes out there and some are in the challenge. Stay in touch if you would like to see how they do

[TCLynx]

There are probably test kits that can read levels of most things in aquaponic water but most of us are not interested in investing in test kits for each element or sending in samples to labs every week for analysis.

 

Most of us just occasionally check nitrates to make sure they are not way too off the chart or to make sure there are some if we are trying to figure out if a problem is lack of nutrients in general or not.  Most other things can be handled with a dose of seaweed extract for trace elements and potassium and sometimes a bit of iron or something else as needed.

 

Now just because a system may not be all that mature for a year, that doesn't mean it won't grow lots of veggies anyway.  It just means that it might not beet a side by side test against a hydroponic system during it's first 6-12 months.  After maturity Aquaponics can often outpace traditional hydroponics.  I grew tomatoes and lots of other greedy things during my first 6 months of aquaponics and that was even with the handycap of pH challenged media.  Now there are many things that will affect aquaponic systems and their ability to grow certain plants well and these issues are usually far more problematic during the first 4-6 months than they will be later.  Like a new system with a high starting pH and likely salting to help the fish past the first nitrite spike is not a good place for strawberries.  Your source water and media choice are going to have a huge impact on the fist season with aquaponics but that does not automatically mean things will suck, some people have none of the normal starter issues and sail right along like clockwork.

 

Just don't expect to plant advanced tomato seedlings the day after you add water to the system and expect them to be producing full tilt within three weeks (remember it usually takes about two weeks to recover from transplant shock and grow new roots and the system even if fishlessly cycled high speed will only be just getting going after three weeks and it takes at least the next three to six weeks to get past the new/just cycled stage.) 

 

Aquaponics takes some patience and even so, it's still much faster than building organic soil.

[Daniel Gunloche]

Localhydro -  Yes I will be watching the challenge - this will be a very good education.  Currently I am using a chemical hydro nute, but plan to be converting to AP soon.

 

TCLynx - I certainly appreciate all your knowledge and input.  Are you saying you would not even supplement a new AP system with even a little organic mix just to help it along?  I still can't see what harm it would do as long as it was minimal and PH and ammonia etc. were monitored. My thinking is that worms and bugs etc. still thrive in soil treated with miracle grow, what harm would something even milder and organic be to an AP system?  You mention "seaweed extract for trace elements and potassium and sometimes a bit of iron"  So is it more beneficial to target some specific weaknesse in the first months than to possably gain toxicity with a complete mix? Would low dosages of organic nutes become a toxicity issue in an AP system?

Thanks a ton...

Dan

 

[Harold Sukhbir]

Hi Daniel,

In AP our wanting to manipulate vs allowing system to grow naturally has some concerns. In AP we use fish meal and also add especially when cycling only micro nutrients. AP is a marine environment with fish and this make the difference. Fish accumulate and then magnify elements to toxic levels as they grow. So what could be harmlessly added in hydroponic solution with plants absorbing what is necessary and leaving behind what is unused in solution to be discarded is not translated the same way in AP. We should be cautious with adding any input because the AP produce ends up on our own tables, besides I've been following all the AP practitioners like TC whose had successful AP for many years and learnt that inputs are not necessary at all. 

[TCLynx]

Good High Quality Fish food does provide most of the necessary elements for growing plants so most of us find that targeting specific lack is more appropriate than doing a buckshot complete fertilizer approach into a recirculating system where certain metals certainly could build up to toxic levels for the fish. 

Also, without knowing the specifics of the "complete fertilizers" I'm NOT going to say it's safe.  I do know of people killing off all their fish by using some fertilizer or other to help give their plants a boost the week before a garden tour and then they have the whole embarrassment of everyone getting to see their system sans fish.

 

Now just because something is "organic" doesn't automatically mean it's "safe" and chemical fertilizers may be safe or unsafe as well, there is no generalization we can make just on that.  Many of the organic fertilizers are going to increase the biological oxygen demand of the system to break them down and convert them to plant usable form and if the system is already at it's limit keeping up with the fish, even small amounts of organic nutrients may rob oxygen and or cause ammonia and nitrite spikes enough to kill fish.

 

I'm not saying it can't be done but I am saying you will have to do lots of research into the fertilizers and how they are likely to react with the system and what they contain to make sure you are not going to be elevating certain elements like copper and zinc to fish dangerous levels.  Fish waste usually provides plenty of nitrogen and phosphorus so you want to avoid adding lots extra of that so you should probably get additional test kits to help you track things like phosphorus, zinc, copper, Iron, and many other things if you feel this experiment is worth it.

[Daniel Gunloche]

Well thank you all,  What I am gathering here is that the system is somewhat simple, but delicate nonetheless and needs to be left to it's own natural biological processes.  I have done tons of research online and bought both of Murray's DVDs but I have not seen any articles or videos that really stress much of this.  It seems important but also seems to be overlooked and understressed in everything I have seen on the subject.

Another question if I may...  With NFT or raft systems, I am planning on using 1:1 or maybe as low as 0.5:1 ratio beds to tank volume for processing solids, then using the effluent from that to run to nft and raft.  This would eliminate the need for the swirl filters, spaghetti filters and dealing with the resulting solids.  In order to minimize sq. footage used for media beds I am planning on going 24" deep, or more for them.  TCLynx - I believe you were talking about how you have had good results with 24" deep beds, do you think they could even be 36" deep for getting the volume to process solids or is there a concern at some point about anarobic areas?  Would this not be a much easier way to process the solids out, and of course fulfill the nitrogen cycle for a raft system?   My plans are to perpetuate my tomato crop year round, and have concerns about what I have seen with large indeterminate tomatoes creating anarobic areas in media.  My thinking is to do them in a raft system, with a vine suspension system above. I have been a mechanical designer all my life by trade, and my idea is to have indeterminate vines 24" on-center in ALL directions (no isles) in the heated greenhouse, with the channels mounted on perpendicular tracks.  There would be only one isle for maybe 20 channels, and when an isle is slected for access, the channels would simply clutch to a common winch cable that would slide the channels over to create the isle desired. Therefore I am thinking very narrow NFT channels (maybe 12" for large tomatoes) to keep weight at a minmum so the channels can roll or slide on the tracks.  I hope this makes sense,  I know it would make for maximum density in a conditioned greenhouse. Either that, or has anyone done a raft system that has no isles, but floats the rafts through an area for access/processing to each unit in succession? The problem I see with this is that access to one specific raft would be very difficult, and maybe just not practical.  Why waste all the space in isles?  It is only costly to heat.  What are the smallest channels that have been used in raft?  Sorry if am overloading you guys with questions, but maybe they are ideas worth discussing.   Thanks again, Dan

[TCLynx]

I'm confused about what you mean on the ratio for NFT or Raft being 1:1 or 0.5:1?????  For a pure media based system the 2:1 grow bed to fish tank works very well.  To find out if lessor amounts of media work long term while heavily loaded to replace the swirl filters and stuff you should probably ask Chris Smith, unfortunately he has only started changing his systems over to that in the past year or so and I can't say that there are many systems out there running media beds as the solids filters for their raft/NFT systems long term yet.  I know some people who have done it on small scale backyard systems but I don't know how long they have been running nor how heavy the fish loads are.  Anyway, it is still a new method so we are still learning.

 

Deep beds, I love my 24" deep beds cause I do get plenty of filtration while also having beds at a nice working height without having to spend money building stands sturdy enough to support heavy gravel and water.   What about 36 inch deep beds?  Well you might ask OutbackOzzy over on BYAP, he is building a commercial system for trout and his grow beds are full size IBC's.  Again that system is still under construction so it's hard to say what will happen 7 years from now but his old home system had some full IBC grow beds in operation for at least a couple years and seemed ok.

 

Media beds are still a great way to grow plants and I know of some plants that will clog beds with roots but I cope with that by having seasons so I am not growing the same plants year round in the beds so in the off season the worms can break down the excessive roots of the aggressive plants.

 

Now I'm not quite sure how you will provide enough space for big indeterminate plants while moving them back and forth to have isle ways and still be able to wrap down the vines as they grow.  I expect it is possible to do but remember that air flow is important to tomatoes so if you have plants spaced really close to the point of touching each other you will be at great risk of certain diseases and pests really doing you some major damage.  Also, plants that close together, you will need to be out there cranking the aisle over and walking down each aisle and tending/pruning the plants every day to keep the plants from wrapping leaves around each other and making it very damaging to open the aisles if you put it off.  While I understand that space in a greenhouse is at a premium, I have also learned that if it is not really easy to access parts of your garden, you will not go there and do the tending needed to make it productive enough to warrant the premium space.  Make it easy to access the plants.

I don't know how one would to that kind of method for DWC unless your troughs are of a material where you could put on waders and walk in the water without worry of damaging the liner.  You could float rafts back and forth a bit to create a space to walk between.  I don't think you could move the rafts far because the plants are attached overhead so it isn't like you could float them all over the place.  The rafts lend themselves better to smaller plants that are quick and you can plant a whole raft at one end and float it along and harvest at the other end.  I have seen big greenhouses where the entire floor is a big raft bed and the rafts are placed in on one end and floated along as rafts are harvested out of the other end.  There is enough play so that workers can push rafts apart to walk in and tend rafts in the middle but with the smaller plants there isn't as much daily tending.

 

For rafts, the beds/troughs are usually build on the ground with liner and so they could be just about any size depending on the type of liner used but most of the time they base the size on the convenient sizes to cut the 4x8 foot foam to avoid waste and also appropriate width to use the liner of choice most efficiently.  I've done a raft bed around 34 inches wide so I cut the 4x8 foam into a 4' by 32 inch pieces or into thirds.  Most others do 4' wide raft beds when using liner that comes in 6' wide rolls or if you are using liner in a 10 foot wide roll you could to an 8' wide raft bed.