Backyard Aquaponics
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Good day everyone, I have a 6 months old 200L system consisting of

FT 180L, 2 half barrel (1 raft + 1 media bed),NFT, RFF and small particle filter. 20 tilapias (1/2lb each)

pH 7.0
NO3 60ppm
NO2,NH4 0

1tbsp daily of Fish feed (koi spirulina pellets + some pellets are got from livestock shop)

My bokchoy,choysum,basil and spinach have been doing well in NFT and raft, but growth seems slow in 1/2 in gravel media bed.

Media bed have 2 rows of strawberries that are healthy but no fruits. Cucumber plant, thyme,spinach, beans and snap peas in media bed are slow to develop. Plant leaves in raft and nft are healthy so I don't suspect a K or Fe deficiency.

Any advice would be much appreciated.
Thanks



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How old are the plants? Your plants may be establish their root system to support them selves before growing.

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Hi @Rcmaveric, good to hear from you again. They are about 2 weeks old. Other plants adjust well to dwc. What you say makes a lot of sense. I usually transplant from coco coir or soil which I make sure I rinse off well before transplanting in AP system. Would you say that non leafy greens take a longer time to adjust? Perhaps my medium is too coarse compared to what hydroton could provide in terms of low resistance for roots to expand? Or perhaps gravel gets too hot during day time. Again, thanks for your help

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Just give them time. If going into a media bed I don't rinse the Coco coir. Specially when messing with the roots it will take longer for them to recover due to shock to the roots.

If possible start the seeds in a media for the DWC so you don't have to clean the roots.

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Great suggestions as usual!

I've never had much luck germinating seeds in media. I've sowed coriander and arugula in my media bed which germinated but soon died after experiencing poor growth. i.e. limp, weak to browning.

Could you give me some ideas on how to start seeds so that I can transfer directly to raft or nft please? I haven't found much on the internet other than a seed starter with hydroton, or starting in rock wool. Cheers

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I start my seeds in a mixture of Coco coir and vermiculite. I use those little plant cells from the nursery and placed in a tray to wick up water from the Aquaponics. I don't rinse the roots or anything. I wait until the plants have 2 to 4 true leaves then I pull the plugs out carefully with the help of a spoon or wooden popsicle stick. Plugs go into towers or media beds. For DWC I use a net pot and add some river rocks to put the plug up high enough then fill in around the plug with river rocks. Then I place the net cup into it's raft.

I saw a video yesterday where I a guy use a net pot filled with coarse vermiculite. He would place a seed or two then cover them just a little bit of fine vermiculite. Then place the net pots in a tray of aquaponics water to wick up moisture. It worked well for him.

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That's very smart and informative:) You're just a pool of information.

Need to get my hands on some vermiculite.

I had initially tried to use coco husk in raft bed net cups previously and I think it breeded pathogens. But that also happened before I added a small particles filter, so I'm not entirely sure what caused my plants' stunted growth and eventually death.

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What's your water temp?

My guess is that the growth is slow partly because your water temp is low, unless you have an indoor setup things are still pretty cool where you are. Raised wicking beds will get off to a faster start in spring than AP beds. Fish don't eat as much in AP when the temps are cool and the wicking beds will warm up faster than your AP setup. I use both and I feel like they complement each other.

Edit: Looks like you are growing inside based on another thread and the pics I saw there. Still, check the temp and you might want to post up some pics of the plants just to see if there is any obvious deficiency.

Thank you for your suggestions. Indeed, wicking beds are on my todo list to complement my AP system. And you're right, the water temperature does feel cold. I need to get my hands on some batteries for my infrared gun. Probably from the tv remote

I still have much to learn, and my system is outdoor. Started last October. Your advice is most welcomed

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Hmm, I think I'm going to need some better pics, the angle is making it tough to tell what's going on. A bit to much from the side on those shots. From what I can see though you either have a mix of plant nutrient deficiencies or the camera angle along with the sun is making it look that way. I think it's probably the former because that would make sense if you aren't feeding the fish much at the moment.

I apologize for my poor photography skills :p
I did some research and it seems like I may have a Mg deficiency judging by the yellow leaves and green veins on mature leaves isnt?

In an attempt to raise pH which was a 6.0, and correct what I thought was a K or Fe deficiency; I supplemented on the 25th with:
with 1 tsp Mg, 1.5 tsp Fe, 1.5 tsp K for 185L FT.

I started foliar spray of 1/2 Tbsp to 1L of Mg since yesterday.

Today's water reading:
pH 7.6
NO3 5ppm

Do you wait for pH to drop or perform water change please?

Don't mind the leaf burn on the pictures as my garlic repellent was likely too heavy on the oil content. Recipe: 1 garlic bulb, 1.5L water, 1 Tbsp oil, 1 tsp dish soap.

I'm starting to realize that changes in a small system happens much more quickly, or my buffering is off, or water low on KH.

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+1, yep looks like a magnesium deficiency. See how that treatment turns out - the necrotic spots won't recover but the leaves should change back from being chlorotic between the veins.



I'd probably just wait for the drop to happen on it's own. Your iron may not be available at this pH depending on what type you're using. If the new growth on your plants starts to yellow then do a spray application (or more if needed) since this avoids the pH lockout issue. For right now the plants look like they don't need it, just be aware. The water temp, feeding, and the amount of bacterial activity play a part in how fast the change will happen.

FYI - You probably already know this - Rapid pH changes stress the fish so it's best not to change the pH more than 0.4 pH units at one time.

Thanks for taking the time to write back. I have much to think about, learn and rectify going forward.

I started feeding again today after my NO3 kept staying at the 100+ ppm mark. Finally I tested for 5ppm today after gradually adding more crops, and not feeding probably. I reckon that I need to lower my stock density in order to feed again. That probably has something to do with the nutrient deficiency. I made a rookie mistake with over stocking. My friend and I didn't give it much thought, thinking that the more fish the better for the plants. He is running 2x 800L FT with about 80-90 fishes total with just a half barrel filled with sunshade for filtering, 3 media beds, 1 nft and 1 raft. He is doing exceptionally well and has me scratching my head. Funny how some seem to effortlessly grow healthy crops with AP

I'm currently building a second system from what I have on hand during this confinement so that I can separate the tilapias. Hopefully my system will run better with 7-8 tilapias each. Some of them might have to end up on a plate. I recently collected a dozen fingerlings from my RF.

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With 80 or 90 fish, even at low feeding levels, his plants are getting more nutrients but he might run into problems because of having too many fish later on. We're still in a low feeding time of the year so it's not putting high demand on his system filtration. The water is also cooler so any ammonia that's there is in a less toxic form than it will be later. These systems are about balance so if you're a bit off you can supplement plant nutrients, add fish, add filtration or add plants (or remove any of the above) to get it right.

That's interesting. Yet I'll take it as every system is different.
Thanks for taking the time to reply and sharing your knowledge as usual. It saves me a lot of time and headaches. I try to search the forum, but it's not easy to pinpoint the information I'm looking for sometimes so that's when I create a post. Maybe I'm not using the search engine properly.
I think its evident that I have to separate the fish to a healthier stocking density so that I can start feeding regularly again. Terra also mentioned that I would have issues with this. Thanks again

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