Aquaponic Gardening

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Michael asked me to start a thread about my experience using Maxicrop during cycling, and I'm happy to oblige!  Maxicrop is a liquid seaweed extract that you can also get in a soluable powder form. Using seaweed extract is talked about quite a bit on the Australian forums, but they use a different brand. the purpose for using it is to give your plants food before the nitrates kick in.  Good plant food that is not harmful to the fish.

When I used it last September I actually had a one quart bottle for my 300 gallon tank (probably only filled to 200 gallons).  I couldn't find any instructions for using Maxicrop for cycling, and according to the dilution instructions on the bottle I was going to create a very dilute solution using the entire I dumped the entire thing in.  Turned the water brown for a couple weeks, but my plants were perfectly happy and seemed to have no ill effect on the fish.  

There is also a form with iron, but I avoid that.  I'm super hesitant about adding anything but fish food and the pure liquid seaweed into my system. I'm just not enough of a chemist to feel comfortable with measuring iron additions to the system, and haven't seemed to need any.  This fear has served me well so far.

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Allisyn, I agree with everything TC is saying (except perhaps that I push ammonia a little higher up than she typically does, more like a 2 - 4 so you can get a definite reading on the chart).  I also come from a hydro background, and recently wrote an article for Urban Garden about the main differences between aqua and hydro (if you are interested click here).  One of the hardest thing for someone from a hydro background to get used to is to trust Mother Nature and put the nutrients, boosters, additives, etc. back in the closet!  Aquaponics is in many ways a difficult leap of faith, but with all these living elements (plants, fish, bacteria, and worms) that need to sort of self-assemble into a balanced eco-system it is just too easy to knock it off balance if you start adding new elements in, IMHO.


I bet that just about any fish will get rid of your mosquitoes...what could be yummier than a nice mosquito larvae?!

Oh yea the mosquitoes.  I've used mosquito dunks (the biological ones shaped like a doughnut) to combat mosquitoes in a tank where there were no fish and it never seemed to harm my catfish or tilapia in other parts of the system.

Get away from the man made chemical nutrients sometime used in hydroponics.  When a good worm population gets established in your growbeds thier castings will provide nutrients that the fish water does not provide. 

 I first started a compost to get the end product for my growing processes. At that same time I added some worms to my growbed. I thought they may have died or escaped.  As many members of this site well informed me,  with enough oxygen worms will not drownd. So far all my stuff is growing well but I am seeing small amounts of nutrient difficency on some of my lettuce. It is a slight tanning on of some of the edges. The plants overall look really healthly though.

 With all this informative information on seaweed extract and what nutrient issues I may be having currently due to small worm populations, I will be buying some extract today.  Also if you have seen Murray Hallam's video when he speaks of worms, he has a ton of worms in all his beds.

All these natural additives is why aqaponics is so great for the future of humanity and civilizations!! We are all laying the path for a better world people and that is great!!! Thank you everyone who share so many pictures and experiences on this site!!!

Thanks for all the input.  I will definitely try the wick idea!  I'll lay off the ammonia for a couple of days and see what happens. What (and where) should I get for the pH (needing to come up)?


Where do you find a mosquito dunk, any old hardware store??


Happy Wednesday!

I"ve been getting the mosquito dunks at Lowes or where ever.  They often come in a package of 6 dunks.  They are a biological control.

Active Ingredient is "Bacillus thuringiensis subspecies israelensis solids, spores and insecticidal toxins* .. 10.31%


It kills the mosquito larva in the water by giving them a belly ach that will stop them from eating and kill them in a few days.  It will do nothing to stop the already adult mosquitoes but if the adults lay more eggs in the treated water the larva won't survive.

Thanks again for the info.  The mos dunks are working great and the wicks are doing the job- mostly... probably user error on the ones that require tweeking.   :)  I've backed off adding ammonia per your suggestion and it has definitely helped the amm levels to come WAY down (it was under 1ppm yesterday), but the nitrites are still 5ppm and the nitrates are fluctuating btw 30-50.  Am I just being impatient (this has been going on for weeks now) or is there something else I should be doing to reduce the nitrite level? I'm ready to throw some fish in there already!  Also, any suggestions for fish food (probably mollies)?? Just the flakes you get at the pet store?  As the fish tank is approx 55 gallons, any suggestions for how many fish I should add? I believe the ratio is usually btw 5-7 gal / lb of fish, but those little guys must weigh a half an oz each. Is a million overdoing it? :)

TCLynx said:

I"ve been getting the mosquito dunks at Lowes or where ever.  They often come in a package of 6 dunks.  They are a biological control.

Active Ingredient is "Bacillus thuringiensis subspecies israelensis solids, spores and insecticidal toxins* .. 10.31%


It kills the mosquito larva in the water by giving them a belly ach that will stop them from eating and kill them in a few days.  It will do nothing to stop the already adult mosquitoes but if the adults lay more eggs in the treated water the larva won't survive.

Base your fish stocking more on your filtration capacity.  How much grow bed do you have.  Or you can go by aquarium stocking recommendations that go more by inches of fish per amount of water but I don't know those exact numbers.


Patience.  Once your nitrite drops below 1 ppm you could probably dose the ammonia up to 1 ppm again and see how long it takes for both to drop to 0.  Then dose again until you get to the point of dosing ammonia to 1 ppm and then have both ammonia and nitrite get to 0 within 24 hours.  At that point you are ready for fish.  Otherwise you can wait until bot ammonia and nitrite drop to 0 and add fish before you are totally cycled but you will have to keep testing and being careful with feed after you add the fish in either case.


Patience.  It seems like it's taking a long time but cycling up a new system generally takes 6 weeks under average to good conditions and can take longer if anything is impeding the process (like cold or something else.)

For a little while now, I've been questioning some of the 'rules' of aquaponics.  Like how effective is maxicrop/seasol?  I tried looking up the analysis but to my untrained eye it doesnt look like theres much in it.


Can someone with better knowledge tell me if theres some data proving that maxicrop really does help with root growth?  This all came up again because someone found this link:

which claims that sodium buildup could harm your fish from extended use of maxicrop, but the spec sheet doesnt show sodium?

I can't really offer much on the scientific side of things.  I can say there are vastly different ways of using it though.  I've heard of some one adding several ounces of maxicrop a day to a 30 gallon system and at those rates I actually worry about the build up of salts and other elements that are really only meant as trace elements.  However, for the first season or year of a larger system when one is adding some smaller amount of maxicrop say once every few weeks, I don't believe there is any danger of salt build up.  (for instance my big system, 700 gallon fish tank 1400 gallons of gravel beds, I've been adding perhaps a quart of maxicrop a month and it definitely wasn't causing any problematic salt build up.)


I based the amount of maxicrop to add mostly on the planting space.  I don't remember exactly what the label dosage is but it was something like x# of ounces per gallon of water used over 100 square feet of garden or something like that.  So originally I estimated the amount of square footage of my grow beds roughly and did the math to figure out how much maxicrop I would need if using it by the label.  Then I just added that amount of maxicrop into my grow beds rather than watering it in since the system water would take care of that.


I say DO NOT add maxicrop according to the number of gallons in your system.  As in if the label says use 2 oz per gallon, that is not the dosage for aquaponics.  Read the rest of the sentence that says spread over 100 square feet once a month.


Now with any good organic fertilizers, the analysis can seem rather misleading The fact that they only bother with the big 3 nutrients on most fertilizers NPK is the most misleading part.  Maxicrop provides mostly potassium (which is often lacking in aquaponics) and trace elements which they don't bother listing at the levels provided by seaweed extract.


The higher quality and more complete your fish feed and the more balanced and mature your aquaponic system, the less help seaweed extract is going to be.  I know people who swear by using lots of it for the first season and then it isn't needed once the system is mature (provided the system is well balanced and the fish food high quality.)


As to the salt from seaweed extract, I don't see it being a problem when only small amounts are used seeing as I've added salt to systems on occasion to treat stressed fish and plants will use up small amounts of salt slowly as long as you are not continually adding large amounts.

Hi All,
Here's an article on the benefits of seaweed extract

Thanks for that, Harold...very useful!  

Albert, questioning is always a good thing and this growing method is still so young that the 'rules' will continue to be re-written over please keep it up! As a side note, Dr. Lennard who is featured in the video you link to co-authored the 'rules' document on this site.

IMO TC gave an excellent description of the sane use of seaweed extract in aquaponics and it is exactly how I feel about it ...and I think Dr. Lennard would also agree....

Is Maxicrop with Iron organic?  Sorry if that question has already been asked.

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