Hello,

My mom and dad have a large fiberglass pond, it was a tank battery. 16ft across x 3ft feet deep. 4700gal, i keep telling them a small fountain in the middle is not enough filtration and oxygenation for the 40ish gold fish that were in there. This spring about 20 have passed with clear/white lesions on them also there is moss all over. We just drained and vacuumed out (every year) I know fish get sick when they are stressed, I have 2 aquariums. Could this have anything to do with what I have told them about the pond? My mom wants to get Koi and I told her tonight I didn't think they would live. I have purchased a 1/3hp pump that puts out 725 gpm. What kind of filter should we BUILD. Help please!

Hi Conrad:

Your pond is about the same size as my pond. My husband built a gravity fed filtration system and I do not know anything about the engineering of that. I just know we have a bottom drain and the waste goes into the filter by itself and settles in the bottom of filter before it gets pumped back out as clean water into the pond.

It has four chambers that forces the water flow to go over one chamber and under another then over and under, four chambers all together, with filter matts and larva rocks and bio balls so by the time it gets pumped back in the bad stuff has been settled.

It is 4 foot wide, 8 foot long and 4 foot deep. But the good news is I only have to clean it twice a year.

We have three water falls for oxigenation. One water fall has a seperate pump and the other two waterfalls are how the clean water gets back to the pond.

He found directions on the interenet. Alas, he is done and no longer has anything to do with it, unless a problem occurs.

So, YES, you need filteration and aireation. These fish get to 3 feet sometimes.

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