Pond Fish Die Off

  Quickbeam 09:14 01 Jun 2013

I posted on this 2 or 3 years ago when my brother in law's pond fish all died off over a 2 week period, although we never found out what the cause was as there was no obvious signs of disease on the fish

Now the same has happened to my own over the last 8 days. A smallish pond 150ish gallons, water fall pumped 12 hours a day, 24/7 aeration, Laguna filter & pump with sufficient capacity for a 500+ gallon pond. Plenty of marginal plants and has been healthy for the 12 years since I dug it out and with only a twice a year blanket weed treatment added.

Well, they're all mortuus now, spilt milk and all that. So what do I do now? can I restock after a couple of months and a water treatment, or should I wait until next spring?

  fourm member 11:09 01 Jun 2013

I don't remember the previous thread but I, probably, would have said this, then.

Check for any self-seeded plants that might have contaminated the water. Euphorbia, spurge, is one to look for as it is often spread by birds and is toxic to fish.

  michaelw 11:09 01 Jun 2013

It may be pond parasites.

A heron nicked our 3 goldfish. I'd shooed it away loads of times but it must've waited till I was out.

I think you were right to be worried in another thread about frog spawn being threatened by the prolonged cold icy spell. All mine have disappeared.

  Graham* 11:12 01 Jun 2013

Could be the cold weather - fish don't eat when they're cold.

  Quickbeam 11:56 01 Jun 2013

I've just had a water sample checked the the local aquatic centre, that came out very OK, so he ruled out a water problem.

I bought some Tetra Medifint for parasites and such which he thinks is the most likely cause and thought the unusual spring may be to blame as others have had the same problem after years of a healthy pond life. He also advised me that I can restock within a fortnight.

I'll check the marginals fm for what I didn't plant.

michaelw, most of my frogspawn didn't survive, but I do have a dozen tadpoles developing legs at the moment, I don't think any toad spawn developed beyond the late frost.

  woody 16:23 01 Jun 2013

Some years ago I had a PM done on some of my fish - they found what killed them and the rest were treated - no I did not take them out one by one and asked them to swallow a tablet!

  Forum Editor 19:20 01 Jun 2013

The Medifin should do the trick.

I assume you do partial water changes on a regular basis? Pond fish are basically swimming in their own toilet, and unless you carry out regular water changes phosphates and proteins will accumulate and affect the health of your fish; it will also inhibit growth.

Fish need vitamins and minerals which are contained in tap water.

The best regime is to do a 20% water change every couple of weeks. It's easy to do with a simple syphon hose, and the fish will love the new water - they'll visibly perk up. You'll need to dechlorinate the pond when you do the change. Drinking water is tested daily for signs of the eggs, spores, ova and cysts of various pathogens. If any are found the chlorination dose will be stepped up, and if you happen to do a water change when that has happened you'll introduce a sizable dose of chlorine to the pond.

Lots of people with garden ponds never do water changes, and they wonder why their fish die, or fail to grow. A Koi carp in good health should grow around three inches a year. If that's not happening something's wrong with the water.

  Quickbeam 20:26 01 Jun 2013

"Fish need vitamins and minerals which are contained in tap water."

I've always avoided tap water on account of the chlorination and used water out of the rain water butt. Which is best?

Most of my regular water change is replacing the water lost through the filter backflushing outlet which is quite easy with the Laguna system. The roses that it flushes the effluent onto are doing very well!

  TopCat® 22:57 01 Jun 2013

I have three large capacity water-butts from which I used to take water to top up my large pond. They were cleaned out twice each year and well disinfected but I started to get problems with some of my fish - three or four of them died!

As a consequence I've since relied on de-chlorinated tap water, as the FE suggests, plus heavy rainfall to top up the pond. (Lord knows, we've had copious amounts of the stuff this year already!) Even so, fairly regular water testing is a must for me as the pH reading tends to alter from time to time and is adjusted when this happens. Care has to be taken to adjust the pH (up or down) slowly over a few days so that the fish do not suffer and possibly die. Ammonia readings too should be as close to zero as possible at all times.

Unfortunately this year my whole pond is covered over by a net, because I started to lose fish. The culprit turned out to be, no, not the ubiquitous heron, but a large seagull residing along with many others on the roofs in neighbouing streets. This particular one still visits each day on the off-chance the net had been removed - no chance of that! :)) TC.

  Forum Editor 07:37 02 Jun 2013

"Most of my regular water change is replacing the water lost through the filter backflushing outlet"

That will be fine, provided that the amount of new water added equates to at least 10% per week. It doesn't really matter whether to change the water weekly or monthly, as long as at least 60%/70% is changed in a three month period.

What you want to avoid is small,'topping up' water changes,as this method can actually lead to concentrations of toxins.

  Quickbeam 07:49 02 Jun 2013

It seems that a new water regime is in order for when I restock which I think will be a little longer than I was thinking. Since the fish have gone, the tadpoles have realised that there are no predators in the water so I'm minded to let them leave the water before restocking.

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