Bore Water Pond Problems

Mike Lee · Posted: Sat Feb 18, 2006 11:24 am Post subject: Bore Water Pond Problems

2 months ago I connected a bore to our 1000 litre pond which was till then an 18 month old healthy freshwater (rainwater) pond with 4 Comets, some shrimp and, what I just found out, were some Perch which I had caught from a nearby frehwater river when they were tiny (4-5mm) but had grown to between 2.5cm to 4cm over a year. Plants include several pots of native rush grass, 2 water lillies, a large papyrus and several other species.
After topping up the pond with bore water (which is salty enough to leave a very thin residue of salt on the garden bed after 3 hours of auto irrigation, and tastes just discernibly salty), things did fine immediately. I then ran the bore water more liberally 2-3 times over an hour or so thereby presumably changing the bulk of the volume and initally, the fish appeared OK. I even added 5 smaller shubunkins which appeared to be OK for 2 weeks. However, 2-3 weeks ago the surface began looking a little scummy/bubbly and the comets started to appear very slow and eventually they were so disabled that I could pick them up by hand. I transferred them into a fresh (rain) water vessel and they promptly recovered and when I reintroduced them to the pond, they became ill again, developing bubbles/ white dots on their fins. They are presently doing well in freshwater again.
Then the perch began appearing at the surface (usually very shy) and dying (4-5 in total) and the shubunkins followed. The surface was very scummy so I ran the bore water twice to clear it but scum appeared soon after (24-48hrs). Thinking all the fauna was gone, I partially emptied the pond only to find 4 smaller Perch (3cm) alive and well, as well as very many shrimp (many tiny so clearly reproducing) and 2 rock crabs that my son caught in a nearby estuary 2 months ago (brackish water) as well as a few tiny baby crabs!
My conclusion is that the water is now so salty that the Comets/shubunkins can't survive and that the 4 small perch still alive (out of Cool

managed to acclimatise.
Is this a correct assumption, and why did the scum/bubbles appear suddenly after 2 months and why is it so difficult to eliminate?
I have always had a 1000 litre/hr pump running through a submerged biological filter but the emerging jet is under and does not break the surface so aeration is not assisted The pond has a large surface area of approx 3 sq m). Has the change in water chemistry caused the filter to fail after 2 months and why did it not appear to do this initially? I have just totally cleaned up the pond gravel/ filter, removed bottom mulch and totally replaced the water with new bore water. I'll have to find a new home for the comets, I suppose, but plan to reintroduce the surviving perch.
Any advice, opinions or solutions would be most appreciated regarding what suddenly caused the scum/bubbly surface after the change to bore water.

ForumAdmin · Site Admin

I think your assumption that the bore water is a different chemistry is correct, I know from experience that ground water is often very high in mineral content, which may explain the subsequent failure (through internal corrosion?) of your pump, and the inability of the comets to adjust. It is not necessarily salt as in marine water salt that is found in bores.

On the scum, sounds like protein build up, usually associated with marine tanks, although my pond has suffered from it. Regular water changes seemed to resolve the problem.

With the high mineral content (assumed) it would be inteesting to monitor if the biological filter was doing just that, or just acting as a mechanical filter.

Mike Lee · Posted: Fri Apr 14, 2006 3:37 am Post subject:

I think the problem may have been a gradual build up of decaying mulch from an overhanging casuarina tree shedding its needles over the year. After the thorough clean, I reintroduced the comets and they are still happy after 2 months. Perch are fine (painfully shy). Saltwater crabs are amazingly doing fine! Will get some new shubunkins soon.

So the lesson is - regularly vaccuum the pond to clear of mulch build up. I have a Pondovac 3 which is excellent.

ForumAdmin · Site Admin

Glad to hear it was all resolved. Be interested in an analysis of the water your using though.

Mike Lee · Posted: Mon May 01, 2006 12:50 pm Post subject:

Haven't had the water analysed but will keep you posted.

We do use the water for irrigating the lawn and it leaves a fine layer of salt on the surface of the soil when dry (I've tasted it).

Seems to have cleaned up the blanketweed problem spectacularly overnight which attests to the validity of using salt in freshwater for the problem (just read the blanketweed post). Lillies aren't doing too well but they never have (pond in shade except in Summer which be another factor).

ForumAdmin · Site Admin

Yes, I to have used salt against blanketweed successfully, but it stunted my lilies as yours. Seems there is always a trade off with these things.