Firstly, you should check out my first blog post about this process which was written about halfway through the cycle. You can find that blog by clicking here>>>

So, presuming you have read the first post now, I thought I would share my results with you. The nitrogen cycle took 4 weeks to complete in my 965-litre aquarium using two large shell off king prawns. I had to use two because the first one completely disintegrated after two and a half weeks.

Nitrogen Cycle Example Graph
Nitrogen Cycle Example Graph

When you start looking into the nitrogen cycle, no doubt you will see a nice stable looking chart, as this example shows.

You start testing your water, expecting your numbers to look like that chart with slow and steady increases in the ammonia, followed by nitrite, then finally nitrate. The reality of the cycle is that it doesn’t happen like that. It peaks and troughs every day, but the peaks just become smaller!

Nitrogen Cycle in an Aquarium
Nitrogen Cycle in an aquarium day by day readings

Above is a chart showing you my day by day cycle readings, as you can see, it looks NOTHING like that nice little chart. The green line shows the ammonia, the blue the nitrite and the yellow is the nitrate. I could see from my readings that the numbers were up and down, so I plotted the points on this graph. Seeing it sent me into a panic, what was I doing wrong?

The answer, nothing! I was doing nothing wrong. It was all going swimmingly. How did I know this? I averaged out my weekly readings, and suddenly my numbers started to look like that nice steady graph.

As you can see from the above, once you average the numbers out, it looks a lot more like the example graph. I should note at this point that I didn’t test my water for the first week of the cycle as I knew it was going to be slow and didn’t see the need to waste the test kits. It would also be worth noting that I am using the Red Sea Marine Care Test Kit.

What is different with my cycle is that I have not done a water change and yet my nitrates have still dropped. There are two things that have brought my nitrates down, and some of you may not like the answer to this but here goes…

My nitrates are lowering because I have an established bacteria colony that has established itself naturally and I have not just poured a bottle of bacteria into my tank to start and finish the cycle within a couple of days. Yes, I used a filter starter, but it did not cycle my tank, it just seeded the tank with some of the bacteria required for cycling.

If you start reading up on the “cycle in a bottle” type products you will see that yes, they do cycle your tank instantly BUT they do cause higher nitrates because the bacteria isn’t fully balanced. I know that the bacteria in a bottle suits a lot of people, and I wouldn’t ever knock anyone for using it! Staring at an empty tank for weeks hasn’t exactly been fun, but I truly believe I have a stable tank now thanks to taking the slow route. The thought of doing a 30-50% water change on this tank because it has high nitrates absolutely terrifies me, I’ve no idea where I would keep that much water.

The second thing that has helped reduce my nitrates is adding Chaetomorpha to my sump with a grow light. Chaeto will use nitrates and phosphates to grow, so it will help reduce them. I will have to monitor it as corals do need a bit of nitrate to grow, but short term, this seems to be working.

In my opinion, this was the right way to start this tank. Yes, it has been slow, but it is now stable and pretty much looking after itself. My readings at the end of the cycle are 0ppm ammonia, 0ppm nitrite, 8ppm nitrate, 11dhk alkalinity & 8.0pH.