Freshwater Tank Water

Question
I have a 55 gallon tank with one oscar (6inches), two goldfish (2inches), and a bottom feeder (4inches+).  I have had this tank for 8 months and in the begining it was crystal clear.  Once summer arrived so did the green water.  It doesn't seem to matter how often I change out the water it is green the next day.  We bought test strips and the Nitrate levels are fine, but the hardness of the water is at 25, so it is soft, and the alkalinity is atleast 300, the ph is 8.4.  I started treating the water with a ph decreaser three days ago and it does not seem to be making a difference.  I also dont know how to make the hardness rise.  I am pulling my hair out, we have looked at a green tank now for four months+.  Please help!!!  Geni

Answer
Hi Geni;

Sorry I haven't been able to get to your question until now. The AllExperts system was down on Thursday and I was not around yesterday to even see if it was up again. Frustrating.

The alkaline water is causing the pH to stay up but since the fish are used to it there is no need to change it. The reducer is only going to make the pH fluctuate quickly and that is far more harmful to the fish than a constant higher pH. All the unbalance from it will cause the green water to continue longer too. If you have shells or coral in the tank, take them out. They are adding to the higher alkalinity and causing the pH to remain high.

There are a couple of things you can try that will naturally help the tank to balance it's pH and help get rid of the green water. Get some driftwood for the tank. Driftwood softens the water and causes the pH to naturally and slowly drop. The algae that causes the green water doesn't like that. You may have to weight it down, soak it or boil it for a couple hours to get it to sink down though. Your algae eating fish will love the driftwood too. They like to rasp on wood as they do in their natural environment.

Also add aeration from an airstone hooked to an air pump. More agitation and higher oxygen levels decreases this type of algae as well. In nature, we see green water in stagnant ponds and pools, but rarely in well circulating lakes, streams and rivers.

The goldfish aren't going to be safe with your oscar for very long. As he grows, they will become food for him. You probably already knew that, but I thought I should let you know just in case. ;-)

Your tank is still fairly new and will balance itself over time. Some just take longer like yours. Lucky you! I know how frustrating it is. Been there myself.

If the measures I recommended aren't improving the situation at all in a couple of weeks, let me know and we can try something else.

Followups welcome

At Your Service;
Chris Robbins

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