My fish are suddenly dying ??

[Cindy_Nguyen]

Hi all,
My mum had a pond in her front yard for about 2 years now and it has no filter or pump at all, the waters always green as well. She does weekly changes to it so it doesn't always stay green. We owned about 3 fish in that pond.
Earlier this year she built another pond out of those blue plastic clam shells to bathe dogs in. She used that as a base and added tap water followed by a conditioner and plants. Take note that the plants are aquatic and one of them are lily pads however they are potted. She transferred the fish and got a few more in her new larger pond and all seemed good until we noticed they were coming up to the surface for oxygen and until then we added in an air pump to help the pond. A day after, 3 of them ended up dead and we don't know why. My mother told me that this has happened twice before and she still doesn't know why. She also has no filter in that pond because she assumed the old pond didn't need one so this one wouldn't. I thought it might be the nitrate and ammonia levels due to fish waste? But even with the air pump it seemed like nothing was working ...
does anyone know why they could've died?
Just a note: They all seemed healthy and to be swimming and eating and only occasionally would come up to the surface for oxygen.
I've read that dirt and the chemicals form the plastic of the clam may be the reason..
thanks a lot!

POND DETAILS: we have water lilies, Water Hyacinth and water clovers.

 

[Lisak1]

How big are these "clam shells"? How deep? How much water do they hold? What's your air temperature right now? Fish should never need to come to the surface for air - that's not how they are meant to breathe. Filtration isn't a must in a goldfish pond IF you have enough plants, enough water, keep the fish load light, AND don't overfeed your fish.

More details would be helpful!

 

[sissy]

Welcome and if you have city water it could have been the cause plus water temps and lack of oxygen as they got bigger can do it also .You need a pump and filter the stress of the water changes puts fish under stress .

 

[Meyer Jordan]

Every time new fish are added some die? I would venture to say that adding the new additional fish is putting the fish load at a level higher than the pond can presently support.
If more fish are wanted then the addition of supplemental biofiltration would be required.

 

[CometKeith]

Hi and welcome. You came to the right place. The fact they were coming up for air is a horrible sign. That means there was not enough dissolved oxygen in the water for them to breathe through their gills. Any way you can get the water moving would be good including a pump and filter, an air pump, waterfall, or some other water feature that splashes water into the existing pond.

 

[Magzire]

Poor fishes, some form of circulation is a must!

 

[Clint8aaron]

Hi can anyone tell me what this is ive only just noticed this in my pond

 

[Meyer Jordan]

Those are advanced ulcers. These are a bacterial infection likely caused by parasites. This is also a sign of compromised immune systems in the fish. And this is usually caused by poor water quality.
Do you have any recent numeric water test results?
These fish should be placed in an isolation tank and treated with a wide-spectrum anti-biotic such as tetracycline.