Can phosphate kill fish?

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Aquarium Advice Freak
Apr 12, 2011
Hey folks!

Just wondering if phosphates can kill fish? The reason I ask is because I went to my new LFS today and the guy said they can. However I was told if I was only keeping fish I would only need to test for nitrates, nitrites, PH and ammonia! I want to know as my fish have been dying and all my other parameters have been fine. I got a phosphate test kit today and my phosphates are through the roof!

I'm not sure, but logic would indicate if they were really, really high then yes. I think you'd have to be talking about agricultural runoff level though. I've never tested for it in a freshwater (except maybe when trying to combat beard algae), and only in salt when trying to combat cyano or keeping inverts.
I was running off the charts on my phosphates at one point and it didnt affect my fish at all. I've since gotten it down to about .25, still high but I;m still working on it. lol I started at over 4ppm which is the highest my test kit goes.

Doing alot of water changes can help as well as adding GFO (granular ferric oxide) like rowa phos or something similar.

It can definitely help.
Yeah I got that stuff today. I just put it in my canister filter. I hope it goes down because I have just started keeping corals. All of them seem fine tho but I still can't understand why my fish keep dying? Any clues?
Could be a numer of things. water parameters, temperature flucuations, ph flucations, acclimation of fish, other fish getting them....How long has your tank been up, how did you cycle and what do you have in the tank? Also how big is your tank?
My tank is 25g. I check my water weekly and nothing has been out of the ordinary. My tank has been running for about 2 years but it was only about a year ago I started doing more research and bought an RO/DI unit and liquid test kits. All my parameters seem to b fine. I just got all my levels almost perfect except my nitrates which are just under 10ppm. I just don't know what else it could b?
Just the nitrates being off. No ammonia or nitrites ph is about 8.3 salinity is 1.024 ive lost two gobies a firefish and a lawnmower blenny in the last 3 months. I only have two clowns now and I bought a green chromis today.
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