How much longer is it going to take to cycle my tank.

  • #1
I've been cycling my 29 gallon now for 6 weeks. I'm using the nt labs testing kit and it shows
0 ammonia
4.0 nitrite
40.0 nitrate

The nitrite level isn't going down and it's been pretty high for nearly 2 weeks. I was told having a high nitrite will stall the cycle and I was told I should do a water change. I've already done 2 50% water changes and the nitrite reduced a little but not much. It was originally at the highest it can be (8.0)

I feel the tank is never going to be cycled. I dont know what to do
  • #2
Hi, how are you doing your cycle? are you feeding with ammonia to grow the beneficial bacteria colonies or are you doing a 'fish in' cycle?
  • Thread Starter
  • #3
I've just been adding in fish food as an ammonia source. My ammonia got to 5.0 on my test kit and is now at 0. But my nitrite and nitrate have both been really high for a few weeks
  • #4
OK, doing it with fish food as the ammonia source is probably the hardest way of doing a cycle & in my experience takes longer than using a pure ammonia source as it's difficult to measure & control how much ammonia is being added to the tank, the idea is to add a measured amount of ammonia to around 5ppm & then see how long it takes the bacteria to convert it to nitrite to bring the ammonia back to zero, that should take about 24 hours, once that's happening & you're getting a consistent nitrate reading & the nitrite falls off the tank is cycled then do a good water change to get the nitrites to below 0.25 & once done you're good to add livestock. I'd run tests on your water source if you've not already done so to see what that's putting into the tank especially if it's tap water, some water companies add stuff which can throw a spanner in the works. With the readings you've posted it sounds as though you're close but the BB colony is having problems converting all the nitrite to nitrate & water changes should help with that but check your water source first to see what it's bringing to the party.
  • Thread Starter
  • #5
When I got my first tank back in 2009 I cycled it with fish food and it only took 6 weeks. I'm just confused because I've read other people have similar problems but then they say they add more ammonia. Surely you want the ammonia at 0.
Won't it take even longer to cycle if I start adding ammonia again
  • #6
Doing it with fish food is just fine. It has obviously worked, because your cycle is close to being done. Don't switch methods at this point. There is nothing to be gained from doing so. You're on track.

The nitrite phase of the cycle typically takes the longest time. And that time can vary from tank to tank. In my experience, its normal for a fishless cycle to take up to 8 weeks, unless you are using seasoned media.

You are seeing nitrates, and that's a good sign. Things are happening. All you can do is wait.
  • #7
If you have no fish in there you'll need to add some sort of ammonia source for the BB colony to feed on or it will shrink or even starve & die off & you'll be back to square one. I agree with JTW above don't change your method now, you're close to cycled so just keep going a little longer & I'm sure your tank will get there.
  • #8
What type filter and filter media do you have in your tank? Beneficial bacteria grow best if they have media with a high surface area and good water flow through that media. Sponge filters and HOB filters with sponges have a lot of surface area, so they work well. Some of the HOB filters with replaceable filter cartridges do not have a lot of surface area for bacteria growth. Those cartridges are designed to enhance the profit of the manufacturer as they have to be replaced periodically. You do not have to purchase a new filter, but it is helpful to modify the filter media used in the filter. There are YouTube videos that can show options for doing that.

Your ammonia is at 0 ppm. That is good assuming you are still adding a nitrogen source on a daily basis. You need to add protein (fish food), urea, ammonia or ammonium chloride to you tank every day to feed the bacteria responsible for the nitrogen cycle. When using pure ammonia, you dose 2ppm and the bacteria should covert that to nitrite within 24 hours leaving 0 ammonia. That is why you have to dose again the next day.

If your ammonia is staying at zero with daily addition of fish food, it might be time to add a couple of hardy fish to your tank and switch to a fish-in cycle. That is what I have always done in my tanks. I have never used ammonia in my tanks.

What is the pH in your tank? If the pH is too low, that can cause the cycle to stall. Try to keep the pH above 7.0. Do you have a KH test kit? That can tell you if your alkalinity is too low. You can raise your pH and alkalinity by adding a commercial buffer, but you can also add a pinch of baking soda (sodium bicarbonate). Just be careful not to add too much.
  • #9
Welcome to fishlore GoldieFlame90 .

Something to think about when eventually you have fish in the tank it will be getting a constant supply of ammonia daily from the waste etc from the fish.

What you are doing now is trying to mimic that daily load of ammonia . So you need to keep adding a little each day. Just as if you were feeding fish and they were making the waste every day.

As mentioned above 8 weeks is not unusual.
The tank is getting there , you are just waiting for the colonies to grow in numbers.

You have both kinds of bacteria in the tank/ on the hard surfaces in the tank. Just not enough of them today

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