To filter or not to filter?

[RPackman]

My parents have a pond that had been established for about 30yrs, but I had to re-line it this winter. It is about 8000L, and has 9 fish in it which are the offspring of fish which have been there from the beginning. The pond never had a filter, and I’ve been saying for years that it should really have one because of the fish. However, it also has a ton of wildlife. Certainly usually has at least 2 frogs, and we counted 30 newts last year, plus a grass snake. Should I get them a filter when it has been a fish-cum-wildlife pond? I don’t want young newts getting sucked in to the pump, but then again it may take years before the wildlife feel happy again in the pond as it has been disturbed and it would be better for the fish.

 

[martin-green]

Should I get them a filter when it has been a fish-cum-wildlife pond?

Why?

 

[RPackman]

Because all information available on the internet says fish ponds should be filtered! However I don’t know what is the right thing to do. The bioload from the 9 fish is unlikely to be huge in a pond that size. When the pond was first put in 30 years ago there were more fish, and they would breed and we would see babies. However, they lost most of the fish (quite a few to herons and kingfishers) and now have this core group of survivalist black goldfish that don’t seem to breed. We want to do the best thing for the livestock - I don’t want their fish to be hanging on trying to survive in subpar water, nor do I want to harm the wildlife! There are a lot of plants in the pond around all the margins, plus lots of lilies for floating cover to get the pond net down in the summer and try to keep it cool (the pond is in full sun!)

 

[netsukekoi]

My 2 cents - it is quite a small pond, so will freeze in cold weather and potentially dry up (or at least dry back) during hot summer weather. If it has no fish it will survive and work very well as a wildlife pond and given the various amphibians and plants you mention, it seems to be doing so and any filtration will definitely upset that balance.

Fish will put a load on the pond in terms of excess nutrients and will also compete for food with the other inhabitants (eating many of the smaller ones in the process) and things get worse if you start throwing in handfuls of fishfood.

My suggestion would be to leave it as a wildlife pond and think of herons and kingfishers predating the fish as even better as they are really good wildlife to have there - though the amphibians would not agree with me and, if in summer it gets a bit green and smelly add a small pump solely for aeration and top up occasionally.

 

[martin-green]

available on the internet says fish ponds should be filtered

Yes, it does say that.

When the pond was first put in 30 years ago there were more fish, and they would breed and we would see babies.

...............And it was done like that as they knew no different. (Before the Internet became popular) and was it a problem? no.
Additional filtration should be used if there is high stock level, and or no "natural filtration" or if you want crystal clear water all the time. Since you have only changed the liner, put all the plants back in, I really would not worry about it, but do keep an eye on it. What are the pond dimensions? roughly? I don't think your pond is small. (8000 L)

If you search the www some will ask what is the "pond formula" to get the pond in balance (so they don't need external filters) there is no "secret recipe" but you and your pond seem to be nearly there.

 

[RPackman]

The pond is a sort of kidney bean shaped, surface dimensions 8x15ft, with 3 different “shelves” and a max depth of 2.5ft. The top shelf is full of marginal plants in baskets, and more than 2/3 of the surface is covered with lilies in the summer months. There was a fair amount of crud at the bottom of the pond when we changed the liner and I saved some for the little critters to re-establish, but got rid of most of it. The pond then definitely had a cycle after refilling and I kept the fish out in a tub with regular water changes until I had no ammonia or nitrites in the pond (no water changes in the pond - too big to contemplate doing that! It is a very different volume to my aquariums!)

 

[martin-green]

I figured by the volume that it is not small, and there is NO CHANCE of it ever drying up. With a pond that size, I think the only thing you have to worry about is anything falling in and not being able to get again, to that amends I suggest you add some steady rocks or bricks to a shelf, so the top is just under the waterline.

You haven't got spot on the "balanced pond" but you are close to it, and I wish you luck and every success. Picture?

 

[dw1305]

Hi all,

Because all information available on the internet says fish ponds should be filtered!

And it was done like that as they knew no different. (Before the Internet became popular) and was it a problem? no.
Additional filtration should be used if there is high stock level, and or no "natural filtration" or if you want crystal clear water all the time. Since you have only changed the liner, put all the plants back in,

Agreed fish will survive in ponds without water movement etc. It is possible that the sellers of pond pumps etc might not be entirely dispassionate commentators?

However, they lost most of the fish (quite a few to herons and kingfishers) and now have this core group of survivalist black goldfish that don’t seem to breed.

Natural selection is a wonderful thing, it it the same where I work, the Herons really like "glittery things".

The pond is a sort of kidney bean shaped, surface dimensions 8x15ft, with 3 different “shelves” and a max depth of 2.5ft. The top shelf is full of marginal plants in baskets, and more than 2/3 of the surface is covered with lilies in the summer months.

Perfect, just leave it how it is.

cheers Darrel