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Hi AP folks, here 2 question, i run a NFT system.


Fish tank is IBC, Biofilter (filled with: bottom - Bio balls, then 3 layers of filterpads on top, and special filter for pump, this filter is of course aerated, total contain of biofilter is300 liter). Fish: 25 - 30 Tilapia, total weight 5,5 to 6 kilo) NFT pipes, 5 meters plant holes: 75.

Last measurment (after cleaning biofilter)

Ammonia: 0.5

Nitrite: 1

Nitrate: 10 (drop down from 40)

pH: 7,2

Ammonia and nitrate was always around 0 and 1, never been higher.


Now my first question is about the water coloration. Since 4 days my water changed into dark brown, the smell of water is lightly fishy and smell a little bit old. i cannot see the bottom of the ibc tank anymore. Fish are eating well, 2 times per day, 1% diet. System is running now for 3 weeks, never had the coloration of water before. i cleaned the biofilter and add around 300 liter of new water. Coloration is still brown, here is a pic before and after:

its from left to right 1to 3,5 weeks


My system, when it was not running, but just to give you an idea what it looks like.


And now my 2nd question....what do you think it is, fish waste or mosquito larvae?

i know the picture is not very clear. many small larvaes swimming around....but i just wonder if this is pooh or eggs?


Well, so far my system is running great, crops are doing super well, all im concerned now is the water coloration, and if my system is going to turn over, even the ph, no2, no3 and nh4 are good. hope to hear from you! cheerio! Ben

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My guess is algae for the brown colour (you had high nitrates) thus perhaps shade the fish tank.  The larvae you picture (those little squiggles on the bottom?) can also be midges (larvae often referred to as bloodworm) They are everywhere and will get into a system eventally.
i had a algae problem when i did fishless cycling, the walls of  ibc tank were green, i covered the ibc tank with a black plastic net (on this picture the walls of ibc tank hasnt been painted blue yet, i painted them blue before i put in the fish) and all algaes were gone after 3 or 4 days. i see many micro solids swimming around in the water, like dust. if it would be algaes, what can i do? any problems will occure? for larvae problem....the larvaes are black or transparent. I will add some mosquito fish into the pipe and will see what happens.

A brown water color doesn't worry me but your comment that you can't seen the bottom of the tank is a bit of concern.


The solids I see in the picture just look like waste and solids and midge larva (tiny red worms) tend to hide in the solids or even make little tubes out of them.  Midges are annoying but don't bite.


Mosquito larva swim around in the water and are dark.  I don't know how well mosquito fish will do in pipes though.

thanks TC, i will give the mosqutio fish a chance and the water temperature is very stabile (checked over 3 weeks every day, never got over 30 C. what would you recommend to do in case of  too brown water, as the factors NH4, ph, No2 and No3 are alright.?

Your system water looks good and healthy to me. The color of your water is due to the beneficial bacteria in the water column and you seem to have a good population.The water in my systems looks the same. A slight fish smell is ok. The midge fly larvae(red worms) will eat the decaying organic stuff in your system which is a good thing. Midge flies look almost identical to mosquitoes so be sure not to confuse them. Mosquito larvae are not red and swim in the water instead of sitting on the bottom


You need to plant out your system now!!!!

Thanks Chris. My systems already planted since 1 week after i put in the fish. Its groing very well. I covered the tank more, add an extra filter into my biofilter and .......surprise! Water looks great, very clean, can see the bottom and the color is lightly brown with a touch of fishy sweet smell. I added some mosquito fish into the pipes and biofilter...will see if they can reduce the dirt. Update will come! thanks for help!
Cool sounds good

Hey all, this is how the water in the tank looks today!

i have added some mosquito fish , i couldnt take a picture of them because they were to fast, well, they cleaned the pipe pretty good, we will see how it looks in the next week, here is an update from today:


Hey all, time for the result. Guppies are doing and awesome job. And my lettuce is growing also very well.
looking good

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