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Hi, I set up my system with 250g FT and same ST. Currently I have one grow bed operational which is 1/2 I can tank. I have 13 medium size talaria. Every day for the last two weeks, I test the amonia. It shows that it is one. I drain almost 1/2 of the water in the system and fill it with fresh water, and measure in 24 hours. Now I am doing this twice a day, same reading. I changed 1/2 of the water in the system and waited 2 hours which is enough to cycle all the water in the FT at least twice. Took a reading. It is still one. I have multiple reading equipments. Do they go old. What is missing? What am I doing wrong? Any help is highly appreciated. Thanks

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Are you using the API test kit?

Assuming your GB has cycled and you have a buildup of bacteria you may not be having a problem. First, despite all the helpful information that's available in this forum Tilapia are hardy enough fish to handle moderate ammonia levels. Also if your pH is low you might get higher ammonia readings. The good news is if your pH is 7.0 or lower the ammonia is actually ammonium which is not very harmful to fish. I had the same problems in my early system and did all the water changes but if I were you I'd not worry too much about 1.0 ammonia especially with lower pH. Even now my ammonia is never below .25.

Hello George,

yes, I am using API test kit. I watched the video very intently.  I also watched part 4 about the nitrate.  to be honest, I am really surprise that in video 3, she mentions that she is happy with zero nitrite.  all along, I thought that we are after having high nitrite reading because these are the bacteria that breaks the ammonia into nitrite on its way to nitrate.  can you please clarify, or point me out to more videos's or reading.  I am very serious about mastering this.

When you have low nitrite, usually it means that your biofilter is working well and is quickly converting the nitrite to nitrate.  Generally, what I see in my system is low ammonia and no nitrite with 80 or so nitrate.

High nitrite is more harmful to fish than high ammonia.

What is your result for nitrite?

What is your result for nitrate?

What is your result for PH?

Moe said:

all along, I thought that we are after having high nitrite reading because these are the bacteria that breaks the ammonia into nitrite on its way to nitrate.  can you please clarify, or point me out to more videos's or reading.  I am very serious about mastering this.

i do not have a biofilter.  what do you mean by a biofilter.  I am over seas in the Middle east.  I do not have my reading close by.  But I am curious as to what you mean by a biofilter.


Your biofilter would probably be the media in your grow bed. Bacteria forms on the media and converts the ammonia to nitrites then to nitrates.It takes about 6 weeks to cycle the media and grow the bacteria you need.  You could add an external biofilter but unless you have large fish stocking density it isn't necessary. Check out this video and all the others available from Bright Agrotech.

If your ammonia is high, then you have fish waste coming into your system faster than your nitrifying bacteria can handle it. Try reducing the amount you are feeding your fish until your bacteria colonize to the point where they can keep up.

How long has this system been running?  Also, if you have time to list your nitrite and nitrate levels, that would be helpful too.


here is what I have done so far.  I literally, washed and drained the FT,ST and swirl tank.  I think the Swirl tank had some poop that was accumulating.  I cleaned all this up AND, I put some duckweed in the Sump tank.  The ammonia has been down to zero for the last 10 days.  The nitrate is 20.  the water in the fish tank is so clear.  yesterday, I decided to remove the duckweed from the sump tank and see how the system can hold up.  I also installed a heater which raised the temp.  in less than 20 hours from 61 to 68F.  This morning, I measure the ammonia, it as zero.  BUT the water in the fish tank was getting darker, a lot darker and I could not see the fish.  May be I should post this question in a new post to understand the benefits and side effect of having duckweed in the Sump tank to assist with cleaning and getting rid of ammonia?  can any one share their experience?  thanks

I'm no expert but duckweed should only remove nitrates in the system. The ammonia is converted by the bacteria and sounds like you're doing good there. My water got darker when I added iron to the system. Is the water dark as in dirty or just color? Give it a couple of days and see what happens. Sometimes these things will clear themselves up.

I'm no expert either but I was told by someone on this site that duckweed will cleanup the water of everything.  at one point I had zero of everything and someone read that I had duckweed in the sump tank and suggested for me to remove it.  at any rate.  may be more  reading is a good idea about duckweed.  when the duckweed was in the water.  The water was crystal clear.  I have a 250G IBC for the fish, and I can see the bottom of it very clearly.  within 24 hours of removing the duck weed, the water is "dark".  I do not think it is dirty.  it is dark.  I check the ammonia everyday, if it is zero and I have a good PH close to 7, I am not going to worry about it for now.  Thanks

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