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Has anyone had a problem with stinky water? Like S T I N K Y.


The gravel grow bed is forming string algae and where the water contacts from the outflow it is growing a black like moss. The plants look fine, Corn, Zuccini, water melon. 

Water temp is 84*F during the 105* days we are having here with a slight green tinge to it. I will test the water tomorrow and get back. It has that lake smell but like an old rotting stinking fishing dock. there are apporx 35'ish Tilapia in a 275 gallon tank. 

any Ideas what I need to look into?

Thanks for any suggestions.

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Do you have any aeration or enough?

How much grow bed do you have and what type of grow bed?

Algae should not be able to form in a gravel bed since the water should not flood over the top of the gravel, the top of the gravel should stay dry except right where the water enters the bed.


How many fish in you have in the fish tank just prompts me to ask if you have at least 275 gallons worth of grow bed?


What are you water test results?






Is there any build up of uneaten feed or fish poo in the tank?  How much are you feeding?


Do you have enough aeration?


Have you checked for dead fish down in the bottom of the tank that haven't floated up yet?


How much water are you pumping each hour?


Are you blocking most light from your fish tank?


I expect you are smelling mostly algae and anaerobic spots in the grow bed.  Is it flood and drain?  Or constant flood?

when the front pond begins to smell like that..well, there's a reason it's nicknamed the "death pond". I just make sure I clear out debris from the bottom on a weekly basis. the smell goes away after I do that.
Excess fish food or fish poo rotting and/or going anaerobic can be nasty enough to gag a vulture.  Make sure there are no wet blobs of fish feed anywhere.

Grow bed is pea gravel 6" deep by 32 sq ft.

Water Test results:

pH: 8

Hardness: >425

Alkalinity: ~180-240

NO3: ~near 0

NO2: ~near 0

Ammonia: ~4-5

Feeding about 3x per day about 1 coffee cup of feed. Aeration? see pics for the return water aeration + I have 4 air stones running.

Pumping about 330 g/hr. that's what the pump is rated at.

I have aout 3/4 of the tank shaded as it is under the grow bed.

grow bed is a constant flood sys.


Thanks for all responses.



I measured the flow rate. It took 10s to fill a 1 quart mason jar. So that should figure out to 90 gallons/hr.


I would vacuum out the bottom of the tank and cut down on your feedings to once a day. Maybe even drain down your tank to inspect the bottom.
Well, I was feeding once/day. They ate one of my koi that was in there. SO I increased feeding a bit.

Is the gravel currently 6" deep in that grow bed?  Or is the grow bed only 6" deep?

Looks like the grow bed is only partly filled with gravel.  If you can manage 12 inches deep of gravel you might be ok but only 16 cubic feet of gravel is only enough to grow out about 16 fish.  You want a cubic foot of gravel for each fish you want to grow out to about a pound.


Anyway, STOP FEEDING!!!!!!!  Your system is not cycled and you need to let the bio-filter catch up to the ammonia or you will kill your fish besides having a stinking mess.  Once the ammonia starts going down you should see a nitrite spike and then the nitrite should go down and you will see the nitrates rise.  Keep feeding minimal until both the ammonia and nitrite are down to near trace levels.  Then you will be able to slowly increase feed while watching the ammonia and nitrite and making sure they don't start rising again.


Draining down the tank and cleaning out any gunk is probably a good idea and then top back up with fresh conditioned water (dechlorinated or chloramine neutralized.)


At the moment I'm not worried about the slime on the gravel I saw in the picture.

I am more worried that you really need to be actually pumping closer to 300 gallons per hour since it is advisable to at minimum move the volume of your fish tank each hour.

4 air stone don't tell me much.  I would suggest you want an air pump that can deliver close to 3/4 cubic foot per minute of air to your fish tank since you currently don't have nearly enough water flow to provide the needed aeration.

Bed is 12" deep & 6" of gravel. I drained the tank and am refilling now. Had to; Peee-Uuuuu.

I think I will Add the pump I used to drain the tank to the cycle bed to increase flow. (Until I can change to a larger pump)

I'll measure it later today.

Feed: They are not eating it I can now see. cleaned a bunch out. What is everyone feeding these days & source? I may increase the depth of the bed later today. Too hot here, Im melting...

At 1 cu ft of gravel/fish then I should fill to near 10" to leave A 2" TOP lip. That'd give me 26 2/3 cu ft, so Id only be over by about 5'ish fish. Now how deep in the bed should the water be. 



Im gonna have to increase the return pipe to at least 1". currently 3/4". It couldn't handle the additional water input.


Yep always increase drain size!  (might even be worth going to 1 1/2" pipe for the drain.)


I like to have gravel at close to 12 inches deep and you want the water level at flood height to be about an inch below the top of the gravel.  If you do it that way then you can figure your square footage of grow bed will also equal your cubic footage of grow bed and it makes the calculations much easier.  Then if you are off by only a few fish on the stocking, I wouldn't worry too much.


You are lucky tilapia are durable fish cause most other types of fish you would have killed them already.


Feed.  I've been using aquamax 4000 dense culture feed here is a blog post about feeds and it contains some tips about how to find a place to buy aquamax.  Fish Feed Blog

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