How much oxygen can high phosphates deplete from a aquarium ?

[chad 1079]

Greetings all. So the past couple of months I've had issues with both my 125 and 210 FOWLR tanks. I've lost several fish in both tanks, but there were no visible signs of disease on any of them. Just rapid breathing and usually staying towards the top. I was advised that it was probably gill flukes because they can cause those symptoms. I treated it with Prazipro which as a side affect dropped my PH to mid 7's. So then I of course started adding PH increaser(balance but also seachem 8.3) which they did there jobs. But then the fish were still looking stressed and I had the water retested and my LFS found very high KH(over 300, 17-18) and I was told at those levels it can kill your fish. So after a couple of water changes I got them back down to around 11-12. So I went to back to my LFS to get a few fish since by this point I lost several fish and only had a few fish left in the 125. So I thought I'd try a small school of green chromis which I've always had good luck with in the past. And at first they seemed fine and they all ate. But sure enough with a couple of days I started losing them, and the couple I observed seemed to be breathing hard and staying at the top of the tank like my fish had before. I retested the water and the everything seemed to be fine ( PH 8-8.1, nitrate under 30, no Ammonia, no Nitrite, KH still in the low to mid 200's) so I had no idea except for maybe the tank still had flukes in it so I re-treated with Prazipro(didn't really seem to help). SO I went back and relooked at the test results from my LFS(it's the API aqua spin, they email you the test results) and I did see the Phosphate levels were high (3.8) which until now I never have really worried about unless it was a reef tank. But then I read some where that if your Phosphates are high enough it can also deplete the oxygen in your tank. Is 3.8 high enough that it will do that ?

 

[Spare time]

That alk level wouldn't have affected your fish. Also I have never heard of phosphate relating to oxygen. Where did you read that?

 

[chad 1079]

That alk level wouldn't have affected your fish. Also I have never heard of phosphate relating to oxygen. Where did you read that?

I googled it and read a couple of different things. But I literally just Googled it again "can high phosphates reduce oxygen levels in a saltwater aquarium". And it said yes. But it may not affect it that much, just trying to solve a problem.

 

[Spare time]

I googled it and read a couple of different things. But I literally just Googled it again "can high phosphates reduce oxygen levels in a saltwater aquarium". And it said yes. But it may not affect it that much, just trying to solve a problem.

I think you are refering to "Too much phosphorus can cause increased growth of algae and large aquatic plants, which can result in decreased levels of dissolved oxygen– a process called eutrophication.Jun 9, 2023"


That isn't the phosphate driving oxygen low.

 

[Randy Holmes-Farley]

I googled it and read a couple of different things. But I literally just Googled it again "can high phosphates reduce oxygen levels in a saltwater aquarium". And it said yes. But it may not affect it that much, just trying to solve a problem.

Forget googling and take the advice of an expert chemist: that is ridiculous. There is no mechanism for elevated phosphate in a fowlr or a reef tank to deplete any oxygen.

 

[taricha]

regarding the number of fish repeatedly dying, I would take another look at some water basics. Find another way to confirm salinity, are we dechlorinating tap water? use a reliable salt mix, do regular water changes. Either there's severe fish disease or the water basics are far from ok.

 

[Borat]

If your total dissolved solids exceed 30% - there may be less water volume for oxygen to dissolve.

 

[chad 1079]

regarding the number of fish repeatedly dying, I would take another look at some water basics. Find another way to confirm salinity, are we dechlorinating tap water? use a reliable salt mix, do regular water changes. Either there's severe fish disease or the water basics are far from ok.

Hello, yes right now I'm using tap water and then I use prime to decholrinate it. I've got a basic hydrometer, but I know from when I get it tested @my lfs it runs a couple points low so I account for that. Lately most of the water basics are good. The only thing that's really been out of whack is high KH, high phosphates, and low magnesium. Things that in a fish only tank shouldn't be that big a issue(al though the guys @ my LFS disagree with some people's opinion on here about high KH and Phosphates) . But either way I've addressed or am addressing all the issues(using phosbond and adding magnesium). So hopefully that will take care of the issue. It's weird I've had fish a Long time and I've never seen anything like it. Anyway thanks for input

 

[Pod_01]

I'm using tap water and then I use prime to decholrinate

Just a suggestion, but perhaps get the tap water checked. Maybe there is excess of some element that is toxic to the fish.

Do you also top up with tap water? If yes some elements might be accumulating.

Good luck,

 

[Joekovar]

I've had dKH higher than the Hanna checker will register (20+) for a couple weeks without fatalities. Though when I slack off on testing and the dKH gets around 12-14 for a month or so my yellow tang starts having lateral line issues. That could be coincidence however, as I slack all around when I slack on testing.

I'm curious what your tank temperature is. A few degrees can make a relatively big difference in sea waters capacity for holding dissolved oxygen.

For instance, 80F vs 74F you can see a roughly 15% difference in how much oxygen the water is capable of holding, all other things being optimal.

 

[chad 1079]

Just a suggestion, but perhaps get the tap water checked. Maybe there is excess of some element that is toxic to the fish.

Do you also top up with tap water? If yes some elements might be accumulating.

Good luck,

Ok thanks for the suggestion I'll do that. I've checked my KH and PH at home but nothing else.

 

[chad 1079]

I've had dKH higher than the Hanna checker will register (20+) for a couple weeks without fatalities. Though when I slack off on testing and the dKH gets around 12-14 for a month or so my yellow tang starts having lateral line issues. That could be coincidence however, as I slack all around when I slack on testing.

I'm curious what your tank temperature is. A few degrees can make a relatively big difference in sea waters capacity for holding dissolved oxygen.

For instance, 80F vs 74F you can see a roughly 15% difference in how much oxygen the water is capable of holding, all other things being optimal.

I was keeping it lower 74-76 but recently turned it up it around 78-80. Because I keep reading where SWF like it closer to 80 now, not in the mid 70's. Which way makes a difference in the amount of oxygen being able to be
held ? Higher or lower temps ? Thanks