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I have a 30 gallon tank and have recently been having some issues with it.  It used to be crystal clear all the time and then started to become cloudy and now has changed to green water.  I have used the clear tablets and have done 1/2 water changes and full water changes and nothing is working to clear it up.  It started around the time that I added a few new fish and plants.  I have taken the plants out, thinking maybe there was something on them that started this problem but it still has not cleared up.  The Amonia level is a bit on the high side but nothing I do seems to help.  When I first complete a water change the water clears up but by the next day the water begings to change to a light yellow green primarily towards the bottom of the tank and by the next day all of the water is green and very limited visibility.  I never used to have this problem after changing the water.  Can anyone give me advice on how to clear this up?

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Without a picture, my first guess would be that your system is relatively new, and that the plants in there may not be able to take out all the nutrients in the water, allowing algae to bloom.  My experience have been that new systems, or systems that have got the scaling a bit out, allowing algae to grow, can have green water issues.  Unless your unit is a display aquarium, I will not be too fussed other than ensuring that the water quality remains good for the fish (I am assuming your component ratios are correct here - you stated ammonia is a bit high, but did not say if the system is new.  Continued high ammonia readings could suggest that you are not fully cycled or that the media component is too small).


As the system matures and the plants grow faster, it should prevent too much algal growth.  If the algae is an issue, you can consider the following:

  • Shade the fish tank (if it is not for display)
  • cut your feeding rate a bit, watch the water quality and see if the situation improves when your water quality improves.
  • If you have one, a temporary UV sterilizer added to the fish tank will suppress the algae until the system settles, but is not essential or typical of AP systems.  I use one only in new set-ups.
  • Double check that you are cycled, and that the component ratios are correct. 

Darker water also tend to become a part of some older AP systems.  I have one that looks like it got a barrel of Tetra blackwater extract in it, but the fish are fine and the water quality is perfect.  Many plants leach chemicals into the water over time, but the colour change is described as amber to brown, not algae green

Pea soup stage some people call this.  Make sure you have plenty of added aeration since this pea soup stage can use up all the dissolved oxygen overnight or when it dies off.  Stop doing water changes as this is actually probably perpetuating the problem.

Here is a link to a thread with a link that might help explain some of this

Algae/Green Water Myths and Theorys

You need to make sure your system is taking care of the ammonia and nitrite and get some plants back in there to use up nutrients.

And wrap up that aquarium and block out most of the light to get rid of the algae.  And you want that algae to go die in the grow bed.  It will help stop future algae blooms.  Dead decaying algae in your grow bed or filter will give off chemical compounds that will tend to inhibit future algae growth to an extent.


Unfortunately, it can be a challenge to manage an aquaponics system with the fish tank or fish pond in full light as algae will keep trying to grow if you can't get the plants ahead of it.  Aquaponics water in a nicely matured system is usually going to have a yellow to amber to brown tint to it and this is normal for aquaponics.

First, I would stop using the clear water tablets - adding more chemicals to your system is very likely to cause other problems down the line.

Also, how's the circultaion in the tank? There should be a nice current going in the tank either from the drainage from your growing system (whatever kind that is) or you should have an airstone going in there if there isn't a constant current.

Same thing just happened to a friend of mine and the problem was his water was going stagnant due to poor circulation in the tank.  Added an airstone in the other end (the end that was very still water) and the problem started resolving itself in 24 hours.

If you describe your system more (circulation, do you have an airpump, grow bed type, how new it is) we might be able to offer better suggestions.

If you are using city tap water, use a chlorine-chloramine remover, without neutralizing those chemicals you are sterilizing your system from all beneficial bacteria.


Add your plants, stop feeding your fish.

green water is caused by too many nutrients in your system that the plants cannot absorb.

as mentioned previously make sure you have a plenty of aeration and a good water flow rate.


Run your system and slowly the water will become more stable, when the water quality becomes good, start feeding again but slowly, a little at a time.

Basically you are building a bio-filter that takes time


Hope this helps

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