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Cycling Day 16

Unfortunately, life got in the way and I didn't have time to run tests for a couple of days. It soon became day 16 of the cycle, but we have good news.


As nitrifying bacteria get established and start consuming ammonia, we expect its concentration to start decreasing. I tested it again today and put the results next to the results from day 9:

This appears to be the case. It looks close to 0.50 ppm, which is a significant decrease as we expected. We still need to wait until it reaches zero, since any concentration of ammonia can be harmful. The pellets are still decaying on the sand and they are likely continuing to produce ammonia.


The first kind of bacteria consume ammonia and generate nitrite; we expect its concentration to increase. Here is today's result compared to day 13:

This has definitely increased since our last test. The solution is a bright purple color that looks most like 1.0 ppm to me. You may look at that color and come to a different conclusion but that's OK: the absolute amount is not as important as the fact that it is increasing.


The second and arguably best kind of bacteria consume nitrite which is still a bit toxic and generate nitrate which is the good stuff. We expect nitrate to increase as these bacteria reproduce and do their job. We've only performed a single nitrate test: before we started the cycle, we wanted to be sure it was zero, so let's look at today's results compared to our baseline:

This is great news! Our cycle is moving forward as expected and all of our bacteria are working.

I would interpret this result as 20 ppm of nitrate, which seems a bit high. But, again, we're not concerned about the absolute amount just yet. When the cycle is complete, we will take some steps to reduce the final concentration of nitrate and we'll test with a more accurate test kit to make sure we get it right.

Next Steps

That's all well and good but there are a few things that we need to do now that we know our cycle is underway.


When we started the cycle, I set the heater to 86°F in hopes that would accelerate things. It's hard to say whether it worked since we had trouble with our first bottle of bacteria, but regardless of that, we need to start bringing it down to its final temperature of 78°F. I'm going to start by setting the heater to 84°F and waiting at least a day. We'll do it 2°F at a time so we don't shock our bacteria. We'll keep testing ammonia, nitrite and nitrate along the way to ensure everything is in order and the cycle doesn't stall.

Removing the Pellets

They are still sitting on the sand in the middle of the tank looking fuzzy and less than delicious. To stop them from decaying further and producing more ammonia, I'm going to remove them with a gravel vacuum. I can see that there are some in the caves as well but I won't worry too much about them. The goal is to get rid of as many as possible without causing too much of a disturbance.

The gravel vacuum removes water and since we don't want to introduce new water right now, I'm going to use the filter sock to catch the pellets and allow the water to collect in a bucket by simply placing the end of the gravel vacuum's hose in the filter sock inside the bucket. Once the pellets have been filtered out, we will put the water back in the tank.

Although there are cheaper gravel vacuums, I recommend you get one like the one pictured here for two reasons:

  • It has a suction pump so you never have to accidentally drink tank water when starting a siphon. Believe me, it doesn't taste good.

  • It comes with a clip that secures the hose to the bucket.

This is the first time we're removing water from the tank, so there are some precautions we have to take:

  • First, we have to turn off the ATO. If we don't, it will kick in as soon as the water line drops and will fill up the tank with fresh water causing our salinity to decrease.

  • Next, we have to turn off the return pump. If we don't and we remove too much water, there is a chance it will drain the sump and the pump will run dry. This particular pump claims to have run-dry protection but it's best to never rely on it if it can be avoided.

  • We're also going to unplug the heater. Again, if we remove too much water and the heater ends up dry, it could be damaged.

  • We're going to secure the end of the gravel vacuum's hose to the filter sock and the bucket. You can use any kind of clip you want (plastic is better) but just know that this is the most common cause of water spills in this hobby.

  • Finally, we need to make sure the bucket is clean. Since we're putting the water back in the tank, we don't want it to pick up any soap or other chemicals that could pollute our tank. It's best to have one or two buckets that are only used for the tank and nothing else.

I ended up taking out about 1 gallon of water with the pellets, which disintegrated on their way out.

Cleaning the Filter Media

Before we put the water back in the tank, we're going to clean the filter sock and fiber balls by rinsing them with tap water. I take filter socks to the sink and first spray them with hot tap water on the outside then turn them inside out and do it again. Just make sure that the sink is clean and there are no chemicals or cleaning products on it.

The sock doesn't have to be spotless right now since we're cycling. In practice, it is a good idea to have two socks so that you can quickly take out the dirty one, replace it with a clean one and then wash and dry the dirty one for the next time.

Once they are clean, we're going to put the sock back in the sump chamber and the fiber balls back in the media basket. I've had both of them in the display section of the tank since we removed them to add bacteria. Now, they'll start to do their job again and remove particles from the water.

We'll pour the water back in the tank slowly and then turn back on the return pump and ATO. We'll also plug the heater back in. Before you walk away from one of these chores, look around to make sure everything is on and working properly.

Adjusting Flow

When I set up the return pump I pointed the nozzles at the two front corners of the tank. This seemed like a good idea but ended up creating an area of low flow in the middle of the tank - where the pellets decided to stay. I left it that way since I anticipated that we would remove the left over pellets and I didn't want the flow from the nozzles to spread them around.

Now that the pellets are gone, we want the return nozzles to stir up the water as much as possible so that particles will be lifted and caught in the filter sock. So, I'm going to aim the two nozzles directly forward, in hopes that they will create more water movement between the rocks.

Don't Forget the ATO Reservoir

We're going to make sure the ATO reservoir is full. Since I was busy for a couple of days, it got down to the last gallon. This is not the end of the world, but we need to train ourselves to always check on it.

Break Time

We're on the final stretch of the cycle: we need to get ammonia and nitrite down to zero before we proceed. We need to wait and test while we lower the temperature.

In the meantime, let's take a break from the cycle and talk about quarantining fish.