Where did these phosphates come from?

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twoodrough

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I am having my LFS test my water for my new 10 gallon tank. They have tested 3 times so far (every couple of weeks or so). This time the employee found phosphates at a level 1. The problem is, the tank has no fish or critters in it yet. Just rock and sand and whatever is growing on the rocks. I do not feed anything to the tank at all.

Ammonia is 0, nitrite is 0, nitrate is just a trace, yet phosphates are at 1. SG 1.025. Calcium 450. Kh 7 and dosing reef fusion 2 every other day. pH around 8.1.

I use RO water from the grocery store. I had it tested the first time I used it and it was okay (not great) at 22 TDS. I use instant ocean salt. The mixed water had been sitting in a covered bucket for several days before I used it. I had done a 10% water change the day before this test.

Any ideas of where the phosphates came from? It does not make sense.

Next time I go back I am going to have them test the source water, the water in the bucket and the tank water to see where the phosphates show up. I am coming from the freshwater world and don't want to spend $50 on a black clown until I clear up this issue.
 
What test kit are they using? Was it dead rock before you for it?


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Its not possible to go from 0 to 1.0 in one weeks time frame if your not feeding the tank. Testing error is my call on this one. 0 to 1.0 is a huge leap when nothing is being added, unless your source water went to crap.
 
I had him test the phosphate twice. Same result. I wonder if the previous two people even tested for it? They just left that space blank on their sheet. I assumed they had tested and it was okay. Maybe they saw the tank was cycled, knew I was using RO water, knew I didn't have anything it there, knew I wasn't feeding anything to the tank, so didn't test for it because it should not have been there. Hmmmm....could be.

I got cured live rock from LFS. Cycled with that.

I would be surprised if it was the RO water. That would have to be pretty bad for the store to be selling. But, you never know. That is why I am going to have it tested again. I did start the tank with tap water, but have since done several water changes with RO. I did have them test my tap water but don't have the sheet for it any more. Since I decided to switch to RO I didn't keep it.

I just looked at my tank and thought of something. For my substrate I used play sand that had been in my freshwater tank before this. This sand did cause the tank to start to cycle before the live rock went in, but once it cycled I figured everything is okay to go ahead. But, I wonder if the old sand could be the source of my phosphates and the first two times they looked at my water they didn't test for phosphates? Before I used the sand for my fresh tank I would have rinsed it many many many times before using it in the tank. The fresh tank had been running for a year or so, maybe more, before I decided to switch things up and make it a salt tank.

I always had good water in the fresh tank, but I don't know if they test for phosphates when they test fresh water. When I first had my salt tank tested I also took in the water from my two fresh tanks. They both had 0 ammonia, 0 nitrite, and only traces of nitrate, and they were due for my regular weekly water change the next day. Neither of those tanks has sand substrate.

What do you think? Could the sand substrate account for a 1 phosphate reading? Believe me when I say I probably rinsed it in a bucket 15-20 times and made sure the water was clear before using it. That would have been over a year ago.
 
What test kit was he using? Phosphates IMO really can't be accurately tested for unless you have a low range kit or electronic tester like the Hanna instruments.


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What test kit are they using to measure phosphate? And yes I could see dirty sand causing a nutrient spike, but I would imagine you'd also have an elevated nitrate reading from it as well though.


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I don't know what test they are using. I can ask the next time I go in. I would assume it is a good one given the size and reputation of this LFS.
 
Had all my water tested today. Source water is fine. Mixed salt water is fine. The phosphates are only in the tank. LFS says they are likely leaching out of the live rock and this will continue to happen. Purchased phosguard which they said needs to be changed monthly. They said phosphates won't hurt fish directly, but will cause extra algae and that is not overall good for the tank.
 
That is pretty accurate. Phosguard will absorb as much phosphate as it can quickly, compared to GFO. Once it has absorbed all that it can, it is worthless. This varies on how much phosphate is in the tank. It can last a week, or it can last a month. I usually change it out every 28 days on my reef tank.
 
So how do you know when it is done working? I put 30 ml in my 10 gallon that I know has high phosphates. How do I know when I need to change it?
 
How do I know when it is done and/or needs to be changed? I added 30 ml to my 10 gallon today.
 
When you phosphates stop dropping, you want it out before they start to rise again. Once you see that number start to slow down quite a bit, from dropping, then its about time to replace it.
 
I don't have my own test kit right now. I was having the LFS do that. I will go back in a couple weeks to see where things are. I might consider getting a phosphate test of my own if this is going to be an issue in my tank.
 
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