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Re: Green Water

On Tue, 29 Feb 2000, Steve Pituch wrote:

> I tried changing the water, against
> the recommendations I've read here, and the phosphates in the tap water
> cause the algae to return full force in about 4 days.

The phosphate by itself isn't the problem, but one way to take care of
that part of your problem is to run your tap water through a phosphate
absorber before you use it in your tank.

> I tried my diatom
> filter that cleared the water up to 50 % visibility, but the green returned
> soon after I removed the filter.  I don't want to wait it out as my plants
> are slowly dying from lack of light.  The fish are doing quite well.

A diatom filter should take it out.  You can help your filter along by
adding a flocculent to make the algae cells bunch together.

> The parameters of the aquarium are.
> 75 gallons
> PH 7.0 directly from the tap.  Goes to PH 8.2 without CO2 injection.  When
> the water is really green the PH creeps up to about 7.4.  This is with about
> 4 bubbles per second CO2.
> KH=220 ppm
> GH=110 ppm (?)
> Phosphate=.5 ppm
> ammonia, nitrite, nitrate = 0, but I have tried 15 ml TMG with 1.5 gm K2NO3,
> same results.
> lights are currently two 175 MH pendants.

This is quite a bit of light for a 75 gallon tank and it may make the tank
unusually prone to green water.  This is particularly true for a new tank
where the plants aren't yet well-established.

One method of getting rid of green water is to leave the lights off and
cover the tank for a few days.  The floating algae can't live long without
light, so after a few days you might have clear water again.  Some people
claim this works without damaging their plants.  When I tried darkening
one of my tanks it *definitely* set some of the plants back, and the green
water came back afterwords anyway.  But it works for some people.

> temp night = 75 deg f, end of light period 78 deg f.  duration = 10 hours.
> I just read that someone was successful using a diatom filter.  I have an
> XL.  After about a day, the diatom mixture was pale green, but the water
> would not clear past 50%.  I also read in Innes that potassium permanganate
> will clear green water.  I don't want to hurt the plants, nor fish.
> I was thinking of using an additive to get the PH down into the low sixes.
> I think the CO2 injection can't help below 7.0 because of my water hardness.

pH is not a part of your problem.  If you add something now you're more
likely to make the problem worse than to make it better.

> There is no surface algae anywhere in the tank thanks to 2 SAEs, 4 CAEs, and
> 2 small plecos.
> Any advice would be appreciated.  I just want to get over this so I can grow
> plants.

My most dependable solution is to add a flocculent and filter the algae
out.  That alone could solve your problem *if* all that's needed is for
your plants to get established and competitive.  If not then you will need
to look for and fix other problems that are favoring the algae.

Roger Miller