Backyard Aquaponics
A place to discuss aquaponics

Does compost tea contain the right ingredients to cycle a tank just starting off? I'm thinking of putting plants in the system then adding compost tea for nutrients until the system fully cycles and I add my fish. Does tea have ammonia in it or should I add that separately to grow my bacteria populations?

Compost tea would provide Ammonia as well nutrients, but depending on what sort of compost you use to make the tea, and which method you use (ie: aerobic or anaerobic) the nutrient profile could vary greatly, and more importantly, you could very well be adding undesirable pathogens into your new system, ie: bacteria, fungi, oomycetes (think pythium) etc.

I would be more inclined to simply add a capful of Maxicrop (or Seasol Powerfeed if in Oz) to your system every day, test the Ammonia level the following day, and repeat the process until you get the Amm level up to about 1-2ppm.

Maxicrop contains Ammonia as well as nutrients for your seedlings, and is a tried, proven, safe method for cycling.

You probably will have the best for starting a system using compost, just make sure the compost has gone thru the complete cycle. You can also try Worm, or Mushroom composts. http://compost.css.cornell.edu/microorg.html

Before worrying about the statement of "you could very well be adding undesirable pathogens into your new system, ie: bacteria, fungi, oomycetes (think pythium) etc."

Reminds me of a Fire Marshall who stated "We can build a building using 100% Class A fire rated materials, but what's not fire rated is the people that are going to be using the building"

On another forum, a member wanted to know were he got nematodes in his sand beds. He claimed everything he used was sterile, but when I asked him what did he use to move the sand, he said his shovels and a wheelbarrow, but he didn't sterilize anything before using them. What he had done was use the items for digging in his yard, that transferred the nematodes into his growing media.

Most backyard compost doesn't get hot enough to kill the pathogens so it's legitimate to look at this either way depending on the source of the compost. Would you give someone a blood transfusion with contaminated blood . With good compost that has few pathogens or a well processed vermicompost I'd have no hesitation to say go ahead. Without a good source it might not be a good idea.

FWIW - For a backyarder it's worth knowing that whatever you do it will probably work out in the end. A lot of soil is blowing around in the air and winds up in your system along with those same soil organisms (some good, some bad). That's how bacteria like the nitrifiers we depend on get into an AP system.

The compost is coming from a business that sells it around the area, so he probably does it right. On the other hand I have no control or observation of the process. Since it's my first system, I think I'm going to go with Maxicrop or an equivalent. I can experiment later.

Thanks for the advice!

I know you posted this last month but I'm gonna reply anyway.

Personally, I wouldn't try it directly in the system you want to cycle, it's too hard to get the dose right.
I have a 5 month old tea that's fully cycled but the nitrates are over 1000 ppm, enough to kill plants and fish.
The ammonia before the system cycles is off the chart, like ink
Even when feeding plants with it, I need to use very little or they'l get toxicity.

But using the already cycled tea is easier to cycle another system, I've done that without issue but not with aquaponics though.
If you cycle the tea in a 5 gal bucket, keep it nice and warm with lots of oxygen, it can cycle in as little as 7 days.
Then use that to do a fishless cycle and flush when done. I'm currently doing a fishless cycle with tea in a micro aquaponics. I'll fully flush the system before adding fish. I'll know soon enough if it'l work.