Hi Bob:

I would like to congratulate you on an awesome website on garden ponds! I was wondering if you might be able to answer a few questions about our pond. I will give you a little background information first.

Our pond is one year old and is 10w x 15L x 2ft deep so I think that is 2,150 gallons! We have a 2000 gal pump and a bio-filter/waterfall as you can see by the picture.

We built this out of treated wood and lined it with the pond liner all in one piece and put a 1 ½ inch pluming part in the side of it that connects to the pump. We used 3 x 20” in diameter floor cleaning pads 1 course (black) & 2 not so course (white) which are sitting on an upside down milk crate. I only spay off the pads once a year. Our ph is great, our water looks clear enough to drink I have not tested all other water levels this year yet, but last year they were all 0. The water temperature is around 70 but has gone up to 80 on a couple of days. Our pond probably gets about 5 hours of sunlight and filtered light the rest of the time. I have several marginal plants on the first shelf and 2 water lilies at the bottom.

We have 6 mature gold fish ranging in size between 2 to 4” and about 3 or 4 of last years babies that are just turning gold now and probably about a dozen new babies from this spring. I know this is probably too many fish is they all grow up, so we will have to do something. We have never done a water change or added any kind of chemicals. I feed the fish only what they can eat in 2 min once to twice a day.

We over wintered our fish last year. Oh yes I forgot to tell you we live in Nova Scotia, Canada where we have low temperatures and lots of snow. We lost only one fish and two frogs. We have not had any frogs return this year so far. We are very proud of our pond, as my husband and I are not the handyman/woman type, and we owe thanks to people like you who take the time to educate those of us less fortunate, and for that I THANK YOU! My questions are below:

1. Should I do a water change, as everything appears good? And if so how often and what about city water with chlorine in it?

2. Should I leave the babies and see how many actually get big, or do I do something now with some of them?

3. We introduced two new fish a couple of weeks ago; one of the small ones, but with neat markings had a white cloudy spot on its mouth after about a week in the pond. It would hide a lot and it never ate any of the food I gave the fish. I can’t find it now; would the other fish have eaten it? Thank you for all you do, I hope to hear from you and I hope you enjoy our pond.

Cindy

Hey Cindy,

1) Modest water changes are a good thing, since they replenish the carbonate salts that naturally buffer the water and maintain your pH balance. A 10% change once or twice a week is more than sufficient. Get yourself some Novaqua or similar dechlorinator and pretreat the pond to eliminate the chlorine and chloramines in the tap water. You have a roughly circular pond with an average 6 foot radius. Your formula is pi x radius squared x depth x 7.48 gallons per cu. ft.= 1691 gallons.

2) Your filtration is adequate for goldfish, and at your volume, nowhere near maximum population. Keep your sprats and grow them on. Avoid pet store fish, they are generally loaded with parasites and will spread the evil to your other fish. It is more fun growing your own guys along, anyway. Goldfish are very easy on the ecosystem, and your 1900+ gallons will support 20 or so. Koi are a very different story. Your pond with current filtration might handle 4 or 5 *small* koi (less than 12 inches) before having to seriously upgrade your filtration.

3) Your newbie with the bad mouth is probably dead.

Given where you live, you might think about covering the pond with a poly house during the winter. It is not as critical with goldfish, which tend to be pretty much bombproof. The frogs will dig in and hibernate.

(Answer courtesy Bob Passovoy)