Aquaponic Gardening

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Is it possible to run an aquaponics system temporarily (say 1 month) with out fish, perhaps using ammonia and liquid seaweed as inputs?

I built an outdoor aquaponics set up for my girlfriend's parents at their summer house in Rhode Island (8 sqft growbed, ~50 gallon tank). I started the cycling process yesterday (May 19th). The plan was that her parents would arrive on June 1, when system would be cycled and we could add fish. However, they just informed me that they won't arrive until mid-June, which is about a month away. I can't put the fish in until they arrive (no one there to feed them) but I want to start growing veggies because we've got such a short season (plus I bought seedlings).

I read on the 'Aquaponic Rules of Thumb' page that one can plant the seedlings as soon as you start cycling. The question is, can I get them growing for a month or so without fish? I've got lots of liquid ammonia and a couple jugs of Maxicrop/liquid seaweed. Can I plant the seedlings now and then add regular doses of ammonia and Maxicrop to keep them growing until the fish arrive in mid-June? This would seem to deliver plenty of Nitrate and Potassium, but I'm wondering if there are other trace minerals from fish/fish food that would be missing.


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What are the nitrite levels? And what specific liquid seaweed product did you end up using?

I don't know the nitrite levels. I've never measured them. I might be able to measure it this week if I can go down.

I used Maxicrop Plus Iron for most of the seaweed, although I also added some BioWeed (

I do "worm ponics" for nutrition. Use a tea maker and brew compost tea or vermicast tea and then put in the system. All my designed systems have a tea maker as the bucket siphon. I add compost or vermicast for all the trace elements.


It is really, really important to know what those nitrite levels are if you have fish (fish-less...not so much). Nitrite is toxic to the fish, so it would be important to see where your level is at.

The Bio-weed looks like a run of the mill cold extraction kelp product, (like Kelpak or Maxi-Crop) there don't appear to be any additions of chelated or other metals in that product...I take it you probably didn't use any metal plumbing parts, or have any exposed metal in contact with the system water

Check the nitrites first, see what the test says...You should be able to pick up a test at any old pet/aquarium shop.

Patrick Roche said:

I don't know the nitrite levels. I've never measured them. I might be able to measure it this week if I can go down.

I used Maxicrop Plus Iron for most of the seaweed, although I also added some BioWeed (

I am guessing low oxygen levels or water temperature.

Change out half the water with hose water that has stood for several hours to gas off the chlorine you can put the fish in here to acclimate them and prove the new water is good.  While you're waiting for the water to gas off; re-plumb the system so that it throws the water up in the air for some splashing action like a fountain, swishing just won't do it...  If the water is just flowing from the fish tank into the grow bed and draining back into the fish tank you are going to have DO problems.  You can also add a venturi device generally made for fertilizing and hooking up an air hose instead.  It will suck air into the flow instead of fertilizer.  You can buy them at bLowe's or Home Despot  here is a good link to a discussion a venturi by the one and only Bob Campbell (Wayne's dad)  

As a last resort there are the air stone and pumps, be sure to get a big set up


The ph seems high for introdcing fish from the store. But goldfish love 7.5.

My trip down to test got delayed, but i finally did! Nitrite was 0. The water level was way down. Other levels were as follows, pH = 7.6, Ammonia = 0, Nitrate = 0 (they system has grown really well as you can see below, and without fish, it went through all the nutrient). So my conclusion is it was the lack of oxygen in the water. I've got an air stone in there now and I filled up the tank again with fresh water, so i will try adding new fish again today. I'll keep you posted! I'll also add a bunch of liquid seaweed to get the nitrate back up until the fish can start pumping out the ammonia.

New question thought: cukes are growing great but older leaves are getting some yellowy burntout spots, but veins are still deep green. New leaves look great. There are plenty of male and female flowers. From this website ( i'm thinking it might be potassium deficiency. This surprises me a bit since i was running it for past few months on a mix of ammonia, seaweed, and bit of hummonia (the seaweed has been 'Maxicrop plus Iron' and 'Bioweed' both of which have levels of potassium). In that system, i believe phosphorus is generally the more scarce nutrient. Any thoughts? Tomatoes also look solid but there are some dark spots. Pics below.

In general, the plants have been growing lots though!

Seaweed extract usually won't provide much nitrogen unless you are using one of the ones with fish emulsion or something.

If you have been just running it with seaweed and pure ammonia, then yes phosphorus is probably lacking.

However if you have been running it with hummonia and seaweed extract, there should be enough nitrogen and phosphorus in the pee and that with the seaweed extract means I'm not sure what to recommend.

Vlad might be able to make a recommendation after looking at pictures.  I know cucumbers are supposed to be real nutrient hogs and apparently they need huge amounts of potassium and I think Vlad also mentioned Magnesium.

So perhaps a dash of dolomite lime might be in order?

They are huge nutrient hogs...and root hogs.  I usually have 2 plants in my 15 sq ft bed and then just a few misc lettuce plants to cover the surface.  The bed will be full of roots by the end of the season.  Check the undersides of the leaves for aphids.  Mine usually get the little brown spots like that from them sucking the life out of the leaves!

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