Aquaponics experiment 2013 week #5: system seems to be cycled, great plant growth and one dead fish

Posted on June 14, 2013 in DIY

This was one heck of a week for the aquaponics system. Without me doing very much, it seems that the system has balanced itself out naturally and established a working nitrogen cycle! But this wasn’t without cost, as the fish did have to endure a couple weeks of stress, resulting in one casualty. More on that later.

Chemical testing – we have cycling!

Friday - 06.14.2013

From left to right: pH = 8.2 (high, but stable), ammonia = 0, nitrites = 0, nitrates = 40-80ppm

The most important aspect of an aquaponics system is establishing the nitrogen cycle that naturally converts all of the bad chemicals (ammonia and nitrites) into good chemicals (nitrates). I was under the impression that this process would take at least a month, but for me it seems to have only taken two weeks.

Last week my ammonia levels dropped to zero, but the nitrites were staying very, very high. I was planning to let the nitrites stay high for one week, then add de-ionized salt to the fish tank if it stays high after that. Sure enough, the nitrites remained very high all week – until today!

Today the nitrites dropped to zero, which is pretty amazing to me. I actually tested the water twice, because I thought I must have made a mistake the first time.

Here are the results for each day this week – notice how the 3rd vial from the left is deep purple all week (and last week), but today it turned a light blue. This means that no nitrites are present.

Stunning plant growth

Friday - 06.14.2013 - left bed

The week brought some really amazing growth for the plants – just browse the photos below to see! Last week the plants were still establishing their roots and adapting to the new environment, but that didn’t take very long at all. This week the plants have been growing more than I was expecting.

Today I tasted some of the buttercrunch lettuce (the large, deep-green, loose-leafed plants on the far left) and was surprised by how good it tasted! Next week I will probably harvest some of this lettuce so that they don’t start competing for sunlight.

One dead fish

This week wasn’t all good, though. Sometime last night or this morning one of the catfish died, probably due to the super-high nitrite levels this last week or two. To be honest, I was expecting ALL of the fish to die by now, giving their lives to jump-start the cycling process with their ammonia. So really, one dead fish is not too bad.

Some of the fish have small blisters on their topsides near their top fin, and one or two have blisters on their gills, but they are all feeding very well and are quite lively in the tank.

Hopefully the rest will survive, but if they don’t I can easily fish for some mature catfish at local lakes.