Phosphate. Bad test set or bad LFS?

So I recently went out and bought a API phosphate test set, first reading on the tank .25, couple days later after a major water change .25, started getting curious what was causing the phosphate in the tank so I decided to test my mixed water .25, tested just my ro/di before being mixed .25. So now im like what the..... So i test my tap water .25. So now im at a loss whether the test set is saying .25 to everything, or whether my tap water is legit .25 and so is the ro/di water im buying from my LFS. Does anyone have any insight?

 

In my experience API test kits are just about as accurate as test strips...meaning not accurate in the least. Get another kit, Salifert, Elos, etc., or better yet, a Hanna Phosphate Checker.

 

Sounds about right to me. Appreciate the info.

 

API is fine for some things, but There aren't many remotely accurate hobby grade test kits. There are a few and they are expensive. An API is not one of them. If you get a reading with an API, you are probably in trouble though, but what the actual phosphate level is, is anyones guess, but it probably is quite high.


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I would normally agree, but if tap water, rodi, and tank water all read the same I am hesitant to believe anyone of which is actually high.

 

IME with the junk kits, any phosphate will give a reading, but .25 is usually the lowest it will differentiate. In other words .1, .2, .3 etc... Will all show up about .25. However there is a difference, the kit is just not good enough to distinguish. If you want a quasi-accurate reading, you'll need a Hach, Merk/DD or Hanna checker. Those are about the only 3 decent hobby grade test kits for PO4 that I'm aware of.


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I am going to check with my lfs to see if they have one and will test phosphate for me. I appreciate the insight

 

more often than not, when people have algae, or nutrient issues, they are either using tap water, buying water from an LFS or buying water from one of those walmart RO water machines. Local fish stores are notoriously bad at maintaining their RO/DI filters. Some have even been caught red-handed selling tap water as RO/DI water. I tend not to have much trust in them. An easy, cheaper way to check them is to buy a TDS meter. The TDS meter should be pretty inexpensive and pretty accurate. RO/DI water should read 0 or at least pretty close. If it doesn't, then likely the water does contain phosphate.

 

I have no algae, the store is a very reputable lfs and I have spent a lot of time talking to them about their water and their filter change cycles, they seem very straight forward and like they take care of their systems. I am buying a rodi in the new future just havent yet.

 

I use an API test for phosphate and can tell if it's under 0.25, but that is about how accurate they can get.