Cycling A System - Should You Go Fish?

Aquaponic systems are closed loop systems that replicate the naturally occurring symbiotic relationship between plants and fish.  Fish provide nutrients for the plants and the plants clean the water for the fish.  Like all relationships, this one takes time to develop as well.

Whether you are designing your own system or looking to purchase a prefabricated system you should be aware that it will take some time for your system to function so that fish and plants are both healthy and growing.  The process of establishing this symbiotic relationship is referred to as "cycling".

You can cycle with fish or without fish.  The choice is yours.  Whether you cycle with fish or without fish, you will need to keep an eye on the water chemistry so go ahead and invest in a good water quality test kit.  These kits will allow you to test for pH, ammonia, nitrites, and nitrates.

I have cycled systems both ways and I prefer fishless cycling.  I will admit it:  I am a mushmellow.  It bothers me when fish die.  I feel like I am their steward and when they die I have failed them.  The truth is when you cycle with fish some fish are going to die.  During cycling there will be ammonia and nitrite spikes that will kill fish.  It is a natural part of establishing the system.  Even if they are just the cheap little feeder goldfish from the pet store, it hurts me when they die.  So I like to cycle without the fish.

In fishless cycling you add ammonia to the fish holding tank (that has no fish in it) in an amount sufficient to bring it up to 0.5 ppm.  You then test the water daily until levels fall back below 0.5.  You add ammonia again to bring it up to 0.5 and wait for it to drop.  After a week or two of this you will start to see some nitrites show up.  These are the nitrosomona bacteria that are establishing themselves in the system and will start to convert that ammonia to nitrites.   You should see a big spike in nitrites before the nitrates show up.  Once the nitrates show up that means you have nitro bacters growing in the system. These guys will take nitrite and convert it into nitrate.  Once this cycle is established you can safely add fish to the system. 

The amount of time it takes to cycle a system without fish can vary from 3 to 6 weeks.  Things that affect the cycle time period are water temperature and pH. Keep your water temperatures on the warm side and the pH in the neutral zone. Also, if you start cycling with water straight from the tap, it will have chlorine in it.  This chlorine is there to kill the unsafe bacteria in your drinking water.  It will also kill your nitrifying bacteria.  That means anytime you use straight tap water you are setting yourself back.  Luckily chlorine readily off-gasses and if you let your water stand for 24 hours the chlorine/chloramine will dissipate and you can safely use it in your aquaponic system.  This is especially true when you need to top off an existing system.

Cycling takes patience.  In the mean time, enjoy the plants that you put in your system.  You have to have plants for the cycle to be established, so plant some water loving plants.  Things like basil, mint, and tomato will do well in a system that is not cycled.  This is because they like water and the lack of nitrogen doesn't really bother them.  In fact, if nitrogen levels get too high, tomato plants will grow but not bloom!  Onions are also great plants for cycling. I've even cycled with petunias!

There is another method of fishless cycling that is mostly promoted by men. It is called "pee-ponics" and instead of adding pure ammonia from the store into the system, human urine (referred to as "hummonia") is added to the system.  Don't really understand why men want to pee into their aquaponic systems, but to each their own.

You can speed up cycling by inoculating your system with bacteria from a healthy system that is already established.  This can be done by taking water from the filter of a healthy system or simply taking water from a healthy system.  Be very careful when doing this.  If the system from which you take your water is not healthy, then you have just spread its disease to your system.  If you have one already cycled and well operating aquaponic system, then by all means harvest the bacteria from your existing system to jump-start your new system.

Lastly, you can go to a pet store that deals in aquariums and purchase bacteria in a bottle.  I am not a fan of this because it is pricey and honestly, how long can those bacteria live in a bottle?

How do you cycle?  I'd love to hear your experiences.

Why Round is Better All Around

Just because I haven't been blogging doesn't mean I haven't been busy.  It means I have been too busy to blog!

Here in South Florida, what every one else calls winter is what we call our growing season.  It is the only time when temperatures, humidity levels, and rainfall all fall back into levels that support hearty and healthy plant growth.

In our own aquaponic systems we have mints, onions, peppers, tomatoes, brussels sprouts, eggplant, arugula and endive chugging along.  In soil we have tomatoes and peppers.  Each and everyone has appeared to have had a very merry Christmas and are starting off the new year great.

Things weren't the same over at the Together We Stand gardens.  The aerator to the fish tanks gave up the ghost. Fish croaked (and these fish are tilapia not croakers - a totally different fish but I digress).  Ammonia levels spiked. Fish croaked.  Ammonia levels went higher.  Well you get the picture.  We were stuck in a closed loop of high ammonia levels and dead fish.  Significant water changes were only making a marginal difference.  We lost over 60 fish in one day!  At this rate, this aquaponic garden was not going to survive.  It was time for detective work.

We started with what we knew to be true.  Aeration had been restored.  Dissolved oxygen should not be the culprit. Even after a couple of 60% water changes ammonia levels continued to be off the charts. The fish were not being fed so they weren't making the ammonia and after removing the dead fish the levels did not come down.  There had to be something we were missing....and there was.

The fish tanks in use are designed with grooves on the inside for placing dividers.  The bottom of the tank is a series of three inverted pyramids.  This is supposed to allow the grower to divide the tank into three areas to separate fish of different sizes.  If you don't understand the description, here is a picture (which should be good for at least 1,000 words).

In reality what this actually does is provide a very deep area in which something like a dead fish can settle. Yes folks, that is what turned out to be the source of our ammonia problem.  After draining the tanks down  to about 25% we were able to see the 13 dead fish that had settled in those inverted pyramids.  When the aerator failed, not all the fish that died had floated. Some had settled and that was the source of the ammonia.  Once those areas were cleaned and the tanks refilled, the ammonia levels  went down and stayed down. I don't want to live those 2 days again.  But, with the mystery solved on the third day we were back on track. 

Dr. James Rakocy, the father of aquaponics has always advocated for round fish tanks.  You can't hide in the corners if there aren't any corners.  Now even though these tanks have radius corners at the edges, they still have corners of a sort on the bottom.  So to the adage that tanks should be round, lets add that they should have flat bottoms.

After all, how can your garden survive if the fish themselves can't survive?