Goldfish dying at alarming numbers . . .

lovesgirl

30,000 gal pond
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Hi, we have a 30,000 swim pond with about 150 goldfish in it. Been established since June 2016. Last week we dropped the water level down at least 1/3, probably a bit more than that so we could mortar some rocks. We have a 3 foot wide shelf that is about 8" deep and we dropped the water below that so we could concrete a rock wall that borders this shelf.

We rinsed the rocks a lot and used a pond vac to suck up as much of the water as we could before it ran off into the pond. We kept the waterfall running that has a 10,000 ph pump but the other two smaller pumps we had to turn off due to the water level.

After several days, the mortar was dry so we filled the pond back up with local city tap water. that is what was used to fill the pond to begin with but we do notice at times that there is more chlorine smell in the water than other times. I did not have any dechlorinator on hand at the time either.

So within another day or so we notice the goldfish who usually gather in a large swell when they see us are now . . not to be seen easily. most are scattered around, staying near the bottom and seem very lethargic. I can just reach down and pick one up. Then we notice we got some dead bodies around different plants, etc. Physically they appear fine, other than being dead.

I test the ph with my pond master test kit and the ph card says 7.5 which is a little higher than usual but still normal range. I thought if the lime in the concrete bothered the water it would make the ph spike. I tested ammonia, nitrates, nitrites too and all were well within normal range.

So being a saturday, we took a water sample over to our local aquaria place (not petsmart) and they tested our water and said our ph was very LOW (which was curious because my test said the ph was 7.5, still within good dates and just 5 drops in the tube so nothing to really mess up) and advised us to put in pond salt . .half gallon when we got home, another half at bedtime, and same thing tomorrow, and then next morning. We also had them test for chlorine and they said it was at 0. (I had read that chlorine dissipates after 24 hours . . ) but we also bought dechlorinator and put that in the pond when we got home.

So we did the salt. We also made a salt bath and would catch any fish that seemed to be struggling and put them in a salt bath for a bit and then back into the pond. They would seem to be gasping a little for air and would swim out of my hand but then would roll onto their sides at the top.

So two days later, still finding dead fish every day. yesterday got another 6 out of there that were all about 4-5 inches long and several babies 1 1/2 -2 " long. The ones in there left are not really interested in eating, staying near the bottom, seem to be having trouble breathing. I've checked the ph with my kit again and it came out lower than 7.5, I believe at about 7.0 but I don't know if my kit is accurate because of the test at the aquaria store.

So now we just go out every day and collect bodies . . .very sad. Any suggestions from others out there?
 

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So sorry for your lost. You have a beautiful pond.

My first thought is chlorine. I did the same thing with my indoor tank once (didnt have enough dechlorinator), most of the fish died except 2 and one baby goldfish. The goldfish was almost dead but I put it under air bubble (tiny ones, not big bubbles so not to disturb the fish) and after a few weeks it's alive and well again.

Chlorine damage the gill. So the damage is done. I'd try to put in as much air in the pond as possible. This should help those who got away with less damage to the gill to breath easier and can recover from it.

May be someone will have a different opinion than me, but extra air will not hurt only benefit!
 
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You should post this over on the Illness and Disease forum. I would put chlorine as the prime suspect, but the more eyeballs the better
 
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My guess is a combination of chlorine and low O2. I note you're in NC, so thinking it might be hot and with two of your three pumps off, the O2 levels would have dropped. I'm very sorry for the loss of your fish :(

Your pond is gorgeous!
 

Mmathis

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My first thought was chlorine..... But, and I am not good at all with chemistry, if the KH was low, and the pH was low, could there have been a pH crash? Maybe something from the mortaring process did get into the water..... Just a thought, but I'll leave that for those who actually know about chemistry.

Do you know what your pH normally runs? And do you test for KH when you test?
 
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Definitely chlorine.... always dechlorinate the poor fish... especially if the chlorine is chloramine that breaks into chlorine and ammonia.
 
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Good to see recovery , ur pond is beautiful looks like natural lagoon , do u add colour how its blueish?
 
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