Ponding newbie, koi died, need help!

[kbn316]

Hi all!

We have a ~2500 gallon pond in partial shade that we put in during summer 2017. It's about 12x20 with the deepest area ~4 feet and the shallow side 1 foot. I live in Southern Wisconsin, so cold winters. Our koi and sucker fish survived the first winter and thrived last summer (2018). This spring, all the koi were dead. Even one of my Bullfrogs was dead in the pond.

Maybe it was the very cold winter we had. But I'm wondering about something else: unbeknownst to me, two potted plants got knocked into the pond in the fall (they were on the deck which edges the pond). I think the dogs knocked them in. Both had been treated with Miracle-Gro. Now that it's warming up and I've removed all the dead fish and whatever decaying plant matter I could see, there's a thick coating of stringy/"fuzzy" algae on all the rocks. There's also algae growing up toward the surface, kind of like it has a stem but it's not solid. There's was bubbly green algae about a month ago that I removed with a net, and that hasn't come back.

I tested the water and nitrates/nitrites are close to zero, general hardiness is somewhat low, carbonate hardiness is low, and Ph is 8.0-8.5. I'm also positive there's a lot of sludge at the bottom of the deep end from the plant soil and decaying plants/leaves. Can't see to the bottom to know for sure. The bottom is lined with river rocks.

I've attached a pic of the shallow end to show the algae/sludge.

I want to remove the sludge without emptying/vacuuming, kill the algae, and get it healthy so I can add in more fish. The water does NOT smell or have that pea soup color. After I turned the waterfall on for the first time and the water settled from that, it's pretty clear for a couple feet. But all the rocks and bottom (on the shallow end where I can see to the bottom) are coated in that fuzzy/stringy algae. It's THICK.

How do I restore my pond to remove the algae and make it safe for fish again? I've read about sludge removers but never used it. We added beneficial bacteria last year and know it needs that, but not sure what order to treat the different issues. Should I do a partial water change? Or use algaecide in addition to sludge remover? And in what order should I do this all?

Sorry for the long post, and thanks in advance for any advice! Please ask questions if you need more info.

 

[kbn316]

ACTUALLY...maybe the frog didn't die. I was just reading other threads and saw that they hibernate in the water and can survive freezing?? The one I saw that I thought was dead was at the edge of the shallow end, all sprawled out. I haven't seen it since, either in or out of the water. I figured it decomposed before I had a chance to fish it out. Maybe it was still in hibernation and actually survived? It surely froze solid in that spot, being so shallow!

 

[Lisak1]

I posted a response in the other thread, but I'm glad you started a new one!

Miracle-Gro! I don't think you mentioned that in the other post! That would indeed be feeding the algae! Hmmm... I think I'd be tempted to change out some water to get that out of there. I'm not sure how long it would take for that stuff to be consumed or dissipate.

Do you still have your sucker fish? Are those plecos or something else?

 

[kbn316]

Oh yea, I forgot to mention the Miracle Gro in my response to your post! Do you think that could've killed them, or just the cold winter?

Ugh, I'm not sure if they were plecos or not. My husband got them to eat algae (I think) and he just called them sucker fish. But they died, too. And the frog I thought maybe survived? Nope. He just slid down onto the ledge. Definitely dead. We put in a bunch of snails last year and they seem to have survived. No floaters, anyway, just a couple.

Now that the system has been running for a couple days and the water settled, it's almost crystal clear. We have a pretty powerful pump, our little 3' waterfall roars!

We've never had murky/pea soup water, so I guess the biofiltration is working. We did have some string algae and fuzzy rocks last year, but never the nasty muck and algae that grows up like tiny little trees like this spring.

My gut tells me the Miracle Gro isn't "active" anymore. But who knows, that's just based on the fact that the algae isn't getting worse. Since I skimmed off the floating debris and bright green, bubbly algae, it's been the same. It's mostly brown, if that matters. The only area it's green is the shallow end that currently gets full sun (until my plants get bigger). I have only water lilies in it right now and they look fine. But of course they do...all that fertilizer!

I tested again today and nothing is way out of whack. I dosed it with beneficial bacteria today, too, but now I'm wondering if I jumped the gun. Maybe it's not warm enough for that yet. If the water continues to stay clear and the levels stay good, I'll be happy...except for all the muck and fuzzy algae. I want to see my rocks again!

 

[Lisak1]

Good information.

Sounds like they were plecos - they can't survive below 50 degree water temps so they definitely don't belong in your pond in WI. And their reputation as algae eaters is a bit overblown anyway. They may be helpful in aquariums, but a pond is a much bigger territory. Any hungry fish in a pond will eat algae anyway.

The Miracle-Gro is definitely contributing to your algae, as is any other organic material that might have been in the pond, including those dead fish. I don't know if Miracle Gro ever "goes away" - I don't trust the stuff anywhere in my yard. They have ties to Monsanto and that's all I need to know to avoid buying any of their products. ANYWAY... I'm not sure how you would test to see if it's still active, but I don't think it would harm fish in a one time dose. Did you put Miracle Gro in the pot, or was it that Miracle Gro soil? And the soil is still in the pond?

As your pond bacteria gets more active it will start to aid in the biological filtration and your plants will start to take up the nutrients in the water, so the algae should naturally start slowly disappear. Remember you want SOME algae - that nice fuzzy green stuff that's like carpet on your rocks is part of your filtration system.

I honestly think its as the combination of extreme cold and no way for the gasses to escape your pond that killed your fish, but who knows. Fish mostly stop eating in the winter, but they are still breathing and producing ammonia. Consider a de-icer for the future or maybe even keep the pond running. Your pond is definitely deep enough to overwinter fish.

 

[kbn316]

Oh man, I sure did not know about the Miracle-Gro/Monsanto connection. Bad. News.

I used the fertilizer, not the soil. Makes me really ticked at myself, because I never use chemicals in my gardens/yard. I compost and deal with pests/disease naturally. But these were houseplants that I'd neglected and were stressed...so I figured I'd try the "easy route" to perking then up since it wasn't in the gardens. And then THIS. Ugh!

I'm going to do as you suggested with a partial water change. Does water temp matter for that? We had a beautiful, sunny weekend in the low 70s, and now 49 for the high on Wed. Gotta love Wisconsin's schizophrenic weather.... Should I wait until it's consistently warmer?

And no more koi, at least for awhile. Maybe we'll get some goldfish or something. I'm still really bummed about my fish and don't want to kill anymore. We only had them 1 1/2 summers, but they really grew on me! I never knew fish could have "personalities." They were my swimmy pals, and it sucked bad having to scoop them out. They'd clearly been dead a long time...all bloated and white. All their beautiful colors were gone. And I'm not even sure if "all" if them is out of the pond...they were pretty decomposed. Gross and sad at the same time. And definitely getting a de-icer this year!

Since I have your ear, mind if I ask another question? My husband seems to think it's ok to turn the pumps off overnight. He says he read somewhere that if we put one of the aerators in the top of the waterfall (under the filters and bio-balls), that the oxygen from the aerator is enough to keep the good bacteria alive if the pump is off.

Does this sound remotely plausible to you?? We're both new to ponding, but I think it's a bad idea. I honestly think he's just being cheap! We have an energy-efficient, brand-new pump, so it's not terribly expensive to run. So I think his argument...well...holds no water!

 

[Lisak1]

I know. I just heard we have a potential for snow on Wednesday. It's been a weird one!

I would never recommend turning the pump off. Bacteria die off is one concern. The other is the lack of circulation and oxygenation to the pond. Remind him that the same plants that put off oxygen during the day take up oxygen at night. You waterfall is an important source of aeration. And keeping the water moving keeps aerobic bacteria at bay - that's the bad stuff that you don't want in your pond.

You might also want to consider a pond breather for winter. Many people on this forum use them successfully. I've never used one but after the winter we had am definitely considering getting one for the future. Google it for a good explanation of how they work.

And like you I am done with koi in my pond. Way too sad to pull those big beautiful dead fish out of the pond! Goldfish are so much easier and ours all survived last winter with no problem. We're going to find some pretty shubunkins to add this year to our herd of goldfish and call it good!

 

[kbn316]

Thanks, Lisa! He didn't argue at all with this info...the pump is on to stay.

I'll look into the breather. Anything to not have to go through that heartache again. And oh, shubunkins, I hadn't heard of them until now! I think we'll be adding a few plus regular goldfish! I'll wait a bit until after a partial water change, the pond warms up, and things are back in balance.

Thanks so much for all your advice and insight!!

 

[Lisak1]

No problem! Hang around with us - we love to talk all things pond!

 

[j.w]

@kbn316

 

[snoozer]

Welcome to the forum. I am also in southern Wisconsin and mother nature really has had some serious mood swing this spring. I have used two pond breathers in my 25 x 35 pond for the last three or four years and have not had any issues with losing fish. I also have two small pumps on the shelf that bubble at the surface that i let run all year round. One year, which ended up being brutally cold, i used aerators and lost all 6 of the koi and i don't even know how many of the gold fish. That was a really sad pond year. I sat on the rocks and cried and told my son i wanted the pond gone. I'm glad to say he didn't listen to me and the pond remains.

 

[kbn316]

Thanks! Yea, rough weather around here, indeed. The more I've read posts on this forum, the more I think running 2 aerators + no de-icer/breather were big factors. It was a hard, sad lesson learned for this ponding newbie...

At least I can stop giving my dogs the stinkeye for knocking in those plants! I thought sure that's what killed the fish.

 

[addy1]

We're going to find some pretty shubunkins to add this year to our herd of goldfish and call it good!

And oh, shubunkins, I hadn't heard of them until now!

Welcome to our forum!

Yeah more shubunkin convertees.....They are beautiful I love them.

 

[Lisak1]

You're my shubbie inspiration @addy1 - I just need to find someone who carries some pretty ones!

 

[addy1]

If I knew how to ship I would get some at the hatchery near here and send them to you. They have all different sizes and all are so pretty. And cheap!

Most of the fish in these pictures came from them.