Started new tank - what am I doing wrong?

I had a 20 gallon established tank with a single betta fish. But he recently passed away after having him for 4 years.
So, a few months ago I decided that I wanted to start a 5 gallon tank. I bought the filter before, and put it in back of the one on the 20 gallon tank.
I set up the new tank yesterday, and put in a lot of the gravel from the 20 gallon. Put in the filter that was behind the other one.
A few hours later I tested the water with my test kit, and I had no nitrites no ammonia and nitrates between 20 and 40.
So this morning I did a big water change, and the nitrates were 5 ppm. The ammonia looks to be kinda in between 0 and 25.
I would like to know what am I doing wrong? There are no fish in the tank. I am going to get a betta fish when my tank is ready.

 

Have you tested your water? To me it sounds like your water could contain ammonia.

 

You have to add ammonia to keep the BB alive. You likely had some organic matter (poo, old food) in the filter media and/or gravel that is now decomposing and causing a minor reading of ammonia.

 

I have a very hard time reading ammonia.
It has never looked like the yellow on the card, but it has looked pale yellow. And since the 0.25 green is a pale color, I never know whether it reading 0 or somewhere in-between. As a matter of fact, I just took a picture I was going to post.

 

I just tested my water and it is between 0 and 25

 

I have a very hard time reading ammonia.
It has never looked like the yellow on the card, but it has looked pale yellow. And since the 0.25 green is a pale color, I never know whether it reading 0 or somewhere in-between. As a matter of fact, I just took a picture I was going to post.

The API master test can be tricky with ammonia. Some people never actually see a true 0 even though the tank is clearly cycled. A reading of .25 is within the margin of error and should not be concerning as long as it does not rise. The nitrites should also be 0, if it is not then there could be an actual ammonia presence (Unless the tank is in the early cycling stages). The trick is to test regularly and change the appropriate amount of water regularly.

 

I just tested my water and it is between 0 and 25

Oh I forgot to say I do use prime

 

The API master test can be tricky with ammonia. Some people never actually see a true 0 even though the tank is clearly cycled. A reading of .25 is within the margin of error and should not be concerning as long as it does not rise. The nitrites should also be 0, if it is not then there could be an actual ammonia presence (Unless the tank is in the early cycling stages). The trick is to test regularly and change the appropriate amount of water regularly.

Yeah, that's what I read. You may have even posted it in another thread. Since it is not anywhere near the .25 color I am accepting it as closer to 0. But it would still be nice to see a true yellow sometime.

 

You will need to add ammonia to feed the bacteria so they can grow in numbers. A cycled tank has lots of bacteria, without food the few you have will starve.