Maxi Crop and Chelated Iron

[Grace Sylke]

Again, thanks to you, Murray, I purchased Maxi Crop for my plants; but I haven't used it yet; and I'm thinking I need to. The actual product doesn't speak about vegetables at all which caused me to pause. I also wasn't sure what to do with the Maxi Crop or how much to use; and I wanted to make sure it wouldn't harm my fish. If anyone can share Maxi Crop advice, I would really appreciate it.

We have put Chelated Iron in our beds. We went very easy on it but feel we could use more iron as we have some really pale looking cucumbers. Is Chelated Iron problematic for the fish? The first dose we gave our plants didn't seem to disturb them.

Here's what's happening:
1. My squash (I planted too many) are in the same grow bed as my Cucumbers. I'm getting Cucumbers; but they are very pale in color while my squash are not coming to maturity. They get so far and then die.
2. I've also got tomato plants (very tall ones) in that same bed. They are just starting to flower so I don't know if they're going to produce fruit yet or not.
3. The snap peas I planted in that bed flourished at first, put out a few peas and then all died out. I think the squash and cucumbers were too much for the peas. Is that right?

Thanks in advance, to whomever responds to this post. I remain,

Gratefully Associated with Aquaponics HQ
Grace Sylke
www.AquaponicsUSA.com

[GaryD]

Hi Grace,

It takes about a year for most aquaponics systems to settle down properly. Some of the things that you're experiencing will resolve themselves over time.

Chelated iron will not harm fish. We mix a half a teaspoon (per 1,000 litres) with water in a bucket and pour it into our grow beds. It will resolve some of the yellowing issues but a lack of iron is not the only thing that will cause that problem. You may be short of nitrogen, too.

GaryD

I've never used Maxicrop so I'm unable to comment on whether it is safe for fish or not. I'll have to defer to our US members on that one.

Gary

[nwestwood]

In my system, I have to regularly add calcium, iron, Potassium and Magnesium.

Here are my log notes on what symptoms go with which deficiencies: ( have experienced and corrected all of these)

1) New leaves brown - Potassium
2) Young Leaves yellow (between the veins) with green veins - Generally Iron or Magnesium.
3) Older Leaves yellowing between - Generally Magnesium or Iron.
4) Growing tips, or new growth stunted and shrunken, or old leaves dry up - Nitrogen
5) fruit doesn't set, or small fruits shrivel and drop - Calcium or Iron
6) Tomatoes - blossom end rot - Calcium
7) Cucumbers - leaves scorched, browning around the edges - Potassium

Fruiting plants have the greatest deficiency tendencies. Green leafy plants seem to survive on lower levels.

Easy source of:
1) Magnesium - Epsom Salts/Magnesium Sulfate (grocery store) -
2) Potassium - Potash (garden store)
3) Chelated Iron - (garden store)
4) Calcium Nitrate - (mine came from greenhouse supplier 19% calc, 15% nitrate)

Calcium and Potassium can bind each other, so add these on different weeks.

I have found that my Nitrate level stays below 5 ppm and that while my fish are smaller, they don't produce enough nitrate, so In my aprox. 1000 liter fish tank - 1000 liter grow beds/raft system, I add 1 tablespoon of calcium nitrate every other or every third day. If I don't, all the small cucumbers on my 2 massive plants, shrivel and die.

I add 1 tablespoon of chelated Iron every other week. 1 tablespoon of Potassium and Magnesium every other week, unless I see plant problems.

My system is 6 months old and fruit shriveling of the cucs is the only problem I really see (calcium and iron). Everything else is doing well. We pick 18-24 large Roma tomatoes a week, about 1 head of lettuce daily, and 3-4 massive cucumbers weekly. Which is just right for our family.

Also, keeping your PH down (6.4-6.8) makes a big difference on what the plants can take up.

Of the additives, calcium, iron, magnesium are not generally toxic to fish in higher levels. Potassium can be, so it's the one I'm more careful with. My next purchase is a complete test kit so I can monitor the actual levels of all these nutrients. Right now I can monitor Nitrate and PH of course, and total dissolved solids. but none of the others.

Someday I'll get my input water tested and see what comes in with it. All I know right now is that it's PH 8.0+, my problem is keeping PH down, I use phosphoric acid. As the system has matured, it takes less to keep it down. Most systems have the opposite problem, that it always drops to low.

[bart]

wow thats alot how many ltrs is your system how many fish are there and does anyone know are these chemicals acumilative in the system you did say tablespoons im starting to get yellowing around the edges of my cucumber and bean leaves and thought of adding somthing to the system but was a bit scared to any help would be great regards bart

[nwestwood]

My system has an approx 1000 liter fish tank, about 700 liters of gravel beds (soon to be 1000), and a 750 liter DWC floating raft tank with a 400 liter sump. There is approx 2200 liters of water in the system.

As for fish, well, uumm, I'm kind of on the heavy side. Currently, there are 98 Bluegill (they can go as high as 3 per gallon), 64 hybrid Striped Bass, and 55 Rainbow Trout. They are about 3/4 of the way to pan size and the load is getting more than my present beds can handle, hence the need for one more gravel bed. Likewise, as I have learned, this is a stocking density that is on the high side, to much of gravel beds with no other filtration. I'll eat out some of the fish and keep it down next go round.

I have test kits, so I monitor most levels, none of them are out of control and some like Calcium, Potassium and Iron are always on the low side. I'll have better test kits next week that are designed to test low ranges and will post more hard data in the future. The rule of thumb for adding is to go slow and easy. Add a little today, then a little tomorrow, watch and repeat as needed.

I've also sent water to the lab for complete testing and will publish the results when they get back.

[GaryD]

Hi Neal,

With that number of fish, I'd recommend that you insert a trickling bio-filter into your system pending the addition of another grow bed. It will provide you with additional nitrification capacity and boost your aeration - both of which will be useful given your circumstances.

In fact, given the modest size of your system, I'd propose that you use such a bio-filter in any case.

Gary

[nwestwood]

Thanks for the suggestions Gary. My biggest challenge is that I'm out of space. When I originally sized the system, it was for 3 grow beds and the DWC tank, which takes up all of one side of the green house and has just enough fall to flow from fish tank, to beds to sump. I don't have any room (in-line) for more stuff! I may drop a small pump in the fish tank and create a second loop for the filter that just pumps to the filter and dumps directly back into the tank. I'm home next week, after back to back trips, and will get the 3rd grow bed installed, and see if that buffers the system for awhile, but as the fish continue to grow, I'll have to do something more, or start eating them before they are full size. Next time I'll keep less fish in this system.

[GaryD]

Hi Neal,

The great thing about trickling bio-filters is that they can be integrated into a system in so many ways. Check out my latest blog post......here.

Gary

[nwestwood]

Finally figured out why my system seemed on the edge, and it turned out to not be filtration. My water flow has been going down due to: 1) having to restrict the bypass flow to force the water through the water heater now we are in winter mode, and 2) the large filter box in the sump tank slowly plugging up.

I turned on my backup pump and tripled the flow rate and magically the tank levels of ammonia and nitrites came down and stayed down. The backup mag pump is in a filter bag and the bag tends to plug up with odds and ends where the pump inlet is. I've got to rig a filter box or other device to spread out the input. I've also ordered a couple of filter bags to hang on the end of the drain pipes that flow into the sump to catch the larger stuff.

I suspect this slower flow is also part of my lettuce growth issues (to slow), that and light, with the low flow, the raft tank doesn't get enough flow through it.

I installed a 300 watt LED light panel above the lettuce raft and will report on it in a few weeks. Most LED lights sold out there are junk, but this came recommended and is built for commercial greenhouses. One light is good for 50 sqr feet. I'm running it 14 hours a day and it shines on the raft tank, but also catches part of the grow beds.

Nitrates are climbing again, hopefully the lights will help the plants take up more nitrates and the new grow bed will give me more growing space.

I started testing my new test kits and it looks like everything but the iron works well. I can't seem to get the iron test kit to read right and will have to work on it some more. I'll have a full report in a few weeks.

[lobitonomada]

Howdy boys and girls.
I was having the problem with yellowing plants for long time. I have a DWC system which is very new only a couple of months but my plant were struggling, finally I added some iron to my system and things started to change, I built a shade for my fish tank and I got some maxicrop powder just a couple of days ago, My plants are looking real good and my fish are very happy, my water is looking real good and I can see my fish now, I think that adding an extra cinder box for extra filtration and growing area and now everything is looking beautiful.