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Could my sump tank be robbing my system of nutrients?

We're coming up on 1 year for our system. We're not raising food fish, but designed the system to clean the water for our backyard koi pond & to supplement our garden. I've seen designs go both ways with the sump tank before the grow beds, and after. We decided to place the sump before, with water pumped from the tank into the sump, where solids drop using a whirlpool effect and cleaner water overflows into the beds. Bell siphons return the water from the grow beds to the pond.

With the exception of some algae, which we got under control using barley straw bales, our pond has never been more crystal clear. We have about 30 fish, ranging in size from 4 inches to 14 inches. It is apparent that our main purpose of cleaning the pond has been fulfilled, but we've experienced some other issues with the plants and are thinking of a re-design. I'm wondering if we should move the sump to the back end of the cycle, as it did seem some of our plants were a bit nutrient deficient. Any thoughts?

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Permalink Reply by Ian Cameron on March 3, 2013 at 9:13pm

It seems to me that removing most of your solids before the grow beds defeats the purpose of said grow beds. Namely converting fish waste to usable plant nutrients. Disclaimer...I am not an expert, but I pump everything to my grow beds and my plants are doing fine.

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Permalink Reply by Rob Nash on March 4, 2013 at 5:58am

im with Ian, its best to pump the poop strait to the media beds.. question is ratios... how much water in the tank, what size grow beds... quick math is, Gallons x .266 = sft of media beds... ie. 100 gallons xs .266 = 26.6 sft of grow beds (@12"deep).

and then fish... 1 fish for every 3 - 7 gallons of water. seeing how most koi ponds start in the 250 -300 gallon range, im guessing you need more fish... and finally, pH could be locking out nutes, have you check pH lately?

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Permalink Reply by Hana Bernard on March 4, 2013 at 9:06am

I think we're okay with the growbed/water ratio. We could probably use a few more fish, but I'm worried about over crowding the larger ones. These guys are more like pets & quality of life plays a role in our system. Checking pH is something I hadn't thought of - I will do that today. Thanks for the feedback!

Looks like it might be a GO for a re-design. We built our system as a double-decker, but part of the issue we had with plant growth seems to stem from the lower beds not getting enough light (a point my husband and I argue over). I have been wanting to move them to a more staggered layout or make them all the same level & needed some ammunition to convince him, as I know it will be quite an undertaking. :)