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PostPosted: Sep 22nd, '18, 03:15 
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Hi, I am in the process of cleaning up an abandoned commercial aquaponics system (with no mechanical filtration), and I'm wondering how many of the established plants are ok to remove at one time without spiking the nitrate levels for the fish?

The system has about 30 adult catfish (1--2+ ft long) and about 200 koi (from 8" to 2+ feet). There is one 15' diameter x 4' tall above ground pool with all the koi, and the rest of the system is 10 pools that are approximately 16" deep x 4' wide x 40' ft long (these are approximate measurements). All pools are plumbed in a loop. About 1/2 of the available raft space is filled with plants. Will try to get a few pictures to post.

I would like to remove the plants because they have pests and/or have gone to seed, but my worry is if i yank all the plants, the nitrate levels will quickly become toxic to the fish. I'll be buying test kits soon to check the water quality so i can get some real numbers to go off of.

My hope is to get this system back to "zero" with healthy water and fish and begin planting with a fresh start, though my initial idea was to remove one pool's plants, while starting fresh ones in another to keep the plant numbers in balance. Also, FYI, I'm not trying to turn this into a high output commercial farm, so its likely I won't be fillings all the pools to max capacity.

Thanks in advance for any advice!


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PostPosted: Sep 22nd, '18, 09:16 
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Hi,

Will definitely need photos and an overview of the system before meaningful comment could be made...
how much are media beds and how much simply rafts ?

however couple things in advance

(a) an established media system with a lot of roots will have a lot of solids and probably anaerobic areas. Simple removal of plants *will* result in a spike or change of some form. Having good circulation and large volumes of water does result in lesser risk if the plant removal is progressive and not substantial.

(b) it is better to disconnect an established bed off of the fish tanks / AP pipe circuit before doing anything serious, that way the crud and issues do not end up in the fish tank. Then you can do things quickly and with a bit of short-term effort.

(c) If you have multiple beds/sections then you should do one at a time and get them back in place - having said that for a commercial system you would probably benefit from getting mechanical filtration in place and then simply taking the fish off-line completely as a quasi-aquaculture for a short while while you sort the veg out.

(d) the alternative to (c) is to set up a parallel plant-side and then move across to it progressively while taking others offline. System water will be cycled so it should just be necessary to flush AP system water through for a while.

(e) when mucking around with fish present make sure you have good aeration and circulation in the fish tanks.

In the case of (c) then if the system needs to keep producing then it will need to be staged, whereas if it is currently cost-loss then doing things quickly to get it back to production has merits.

IMO a large or commercial type system would ideally be able to be segregated at any time. So important to have capacity to run the fish side as a quasi-aquaculture (or at least subsist on this basis during horticulture management periods). It is practical to ensure that filtration and aeration options are incorporated in a large or commercial AP - for a variety of reasons.
** but yours does not sound like a commercial enterprise **

>> Also, FYI, I'm not trying to turn this into a high output commercial farm, so its likely I won't be fillings all the pools to max capacity.

The risk is therefore much less. And you will get some protection from having large volumes of water. Which means a lot of the AP 'rules of thumb' probably apply to a lesser extent.

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PostPosted: Oct 5th, '18, 02:34 
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Sorry for the delayed response and thank you for the detailed reply. I have taken measurements of the whole system and have some photos to share.

There are ten long shallow pools measuring in total approximately 635.5' x 4' x 9 inches deep (each pool is about 63' long). these pools have a few dozen adult catfish and lots of catfish guppies.

There is a 12' wide by 42" deep pool (pictured) with many koi.

The system is 100% rafts. I planted some test plants (cabbage and lettuce) and from the looks of their slow growth rates and slight chlorosis on the plants already established in the system, i'm guessing the system might be nitrate depleted. I have not found a test kit yet---if there is a recommended one that is accurate, I'd be interested in checking it out. I have a digital pH meter.

I think that I will opt to plant in one of the empty pools while cleaning out a neighboring one to avoid any nutrient spikes, though I'll need a test kit before going ahead with that.

And thanks for the reminder that the roots will have trapped sediment, we already cleaned one pool out that had been nearly full of anoxic sludge, which in turn meant we had to figure out how to isolate individual pools, so now that we can do that, cleaning should be less dangerous to the fish.

-mike


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PostPosted: Oct 6th, '18, 07:53 
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wow that is big.... Yes, would be nice if you could close off a raft section from the system and clean it out.

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