Apologies for the mundane but we have struggled for 4 years to establish goldfish in our garden pond. The pond is about 1500 litres, the water runs through a filter and uv bulb and is returned via a waterfall. The uv bulb is new and working. The water is generally crystal clear with some stringy algea. We have never had more than ten goldfish in the pond. The only other thing in there is a large Lilly. Every year we lose practically all our fish (just found floating on the top) slowly. We buy more typically early summer and the cycle of loss starts again. The ph seems ok and the ammonia levels negligible. Evaporative water loss is replaced by hose or water butt always with a chlorine treatment. The pond is overhung by apple and pear trees but netted so only very few make it to the water. I thought goldfish were robust but they never seem to last more than a few months in this pond and we are now out of ideas. Any advice really welcome.
Could you post the water results for pH, ammonia, nitrite and nitrate at all? That would help.
I don't have a pond but I suspect lack of 02 when the weather warms up - you say most fish died over the summer - combined with possibly less than ideal water quality, is the cause.
Ammonia readings would also suggest an upgrade is needed to the filter size wise as it seems to be struggling with dealing with the fishies waste. Elevated readings of ammonia will kill fish. Also, the existing waterfall may not be breaking the surface area enough to assist with gaseous exchange. Some form of large air stone/larger waterfall feature may assist with the lack of o2.
The pondy's I'm sure will be on later (2010 knows his stuff) so I hope FK can help you with this
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Hi. Many thanks for the interest. Pond dimensions: approximately 2 m long, 1 m wide and half a metre deep. I have sampled the water again today: ammonia aprox. 0.2 mg/L; nitrate approx. 3 mg/L; pH 8.3 I guess pH may be a problem? If so any advice as to possible cause and treatment hugely welcome. I have asked two local aquatic centres and neither seem to think a pond aerator to be anything other than a waste of time (of course they could be wrong). The water is not scrubbed of ammonia or nitrate: it circulates through an Oase Pump and filtration foams via a UV bulb. It was what has always been recommend to us.
When you say you buy more Goldies in summer, just when do your fish die?
Im thinking the depth of the pond may be an issue; 50cm is not really enough depth to protect your fish over the harsh winter months, the deeper the pond the warmer the water stays at the bottom. Fish will stop eating when it gets cold as they go into semi hibernation which slows their system down and conserves energy until it warms up again, im thinking that they may be suffering whilst in hibernation because they don?t have the depth to retreat to which in turn could weaken their immune system.
Also, how do you clean your filter and how often? Do you have your latest water reading for NitrIte?
I wouldn?t worry about the PH too much, goldies are very forgiving of this but it does seem to be quite high. If you stand a beaker of tap water for 24 hours to let the temporary gasses escape them take a PH reading this will give you an idea of what your pond should be or there abouts. If there is a big difference, is there something that could be raising the PH of the pond? such as edging stones maybe!
Hi many thanks. I have never tested nitrite, only nitrate. In fact no one has eve suggested that we need to. The pond is lined with a pond liner with some rocks accessing the water but not many. We typically replenish the pond spring time but will typically lose most of these fish by Christmas. The pond has never frozen and I don't thin the issue is temperature related. The deep part of the pond is about a metre deep. 0.5 m is the average depth (there are 3 "layers"). I could completely rebuild it and make it deeper everywhere butbthat is a truly huge job and we are talking about just goldfish not Koi so I am still bemused as to why we struggle. Literature seems to suggest that, as you say, the pH is probably ok and indeed I have found no suggestions for lowering it anyway. The sponge filters in the Oase pump system are "cleaned" by compressing them while flushing the pump - I do this once a week.
Do you use tap water or pond water to flush the pump and clean the sponges?
Your filter really shouldn?t need such a thorough clean, i would suggest once a month-6 weeks should be about right, using pond water only as the chlorine and chloramines in tap water will kill your filter on contact.
Hi, thanks again. I use pond water only. I periodically top up with mains or water butt water but use a dechlorinator when the former. The only suggestions thus far, then, seem to be to test for nitrite. Presumably if nitrite is high the only solution is a partial wateor change?Everything else seems spot on? Any other suggestions welcome.
Hi JJD, You say that you have never had more than 10 fish in the pond, and these don't last very long and are replaced every year. Roughly how large are the fish?
If the fish are quite small I'm wondering if the filters have never become properly established due to a small waste load?
Another possibility might be the food that you are using. You say that there is nothing in the pond apart from one lilly, therefore there won't be much in the way of a natural ecosystem, and your fish will be totally reliant on the food that you are giving them. I can't guarantee that it will solve your problem but adding additional plants certainly won't do any harm.
As others have eluded to the most common cause of problems in a pond is water quality. I would recommend that you take a sample of your pond water (in a sterile container) to your local specialist fish supplier and ask them to test it for you. Most specialist shops offer a water testing service and they will be able to test all parameters for you. There will be a small charge for this service but they just might spot something that you are missing.
One final suggestion, is it possible that any chemicals from garden fertilisers, weedkillers etc could get into the water? do you spray the overhanging trees? Most garden chemicals are highly poisonous to fish.
Sorry this is more questions than answers but hope that it may help.
Hi iain, many thanks for taking the time. The fish something like 2-3 inches long typically. The overhanging trees have never been sprayed with anything. I did upload the water testing that I did at the weekend. I could feed them more often; I only give them a few granules every couple of weeks. Our local fish place suggested they need practically nothing. Maybe this is a mistake? From the responses so far there seems to be nothing else obvious other than maybe an aerator and maybe some more plants. The trouble is it's all maybe's and more time and money and it's "only" goldfish so I am really surprised this is seemingly so difficult. JJD