Merck test kit questions.

[PowermanKW]

So I got a Merck, and found the low end to not be very good with color differences. I was looking at the test tubes on their own and could not see a good match. tried better lighting no difference.

Then I used the styrofoam block. Was not appearant I had too. Well that was much better. I expected that my PO was lower... but using this method, it matched pretty good with .14 PO4/3. So is this the way it is supposed to be done?

Having said that I ran a batch of GFO, now I'm on my second batch. 1.5 cups of BRS GFO on my 90g. I'll see if it drops. Is .14 bad for SPS...cause mine seems to be doing well. Color, PE... will things get better? How much will GFO drop these... I mean a month, 2 months, 6 months....

[HighlandReefer]

Putting a pure white background behind the test tubes is a good way to help determine the colors and provides a more consistent interpretation of the color. ;)

GFO can be exhausted quickly when you are in the process of reducing phosphate. I would change it out weekly until your levels are closer to 0.03 ppm. It does take time to reduce the levels. In your situation it might be over a month or even longer, depending on how often you change the GFO out. Certainly longer if you decide to replace the GFO monthly. ;)

[PowermanKW]

That's cool. That has been quite puzzling to me at how fast GFO is exhausted. I've seen test on GAC and how fast it can clear, but nothing really on GFO. So BRS says 4-8 weeks, but don't know if it exhausts in a linnear fassion or not. So if I change in two weeks how much "good" GFO am I throwing away.


On the Merck test, you have the long test tubes looked at from the end with the cap off. It has a blank sample to put ove rthe color dot, then the test sample over a white dot. I just didn't know if I was supposed to put them in a block they provide, but the block gives a much better match than without.

[HighlandReefer]

Testing the effluent from your phosphate reactor with high grade test kit or photometer is one way you might be able to tell how fast to change the GFO out. You will have to test the effluent right after changing your GFO and then use this as a gage to make a decision as to when to change it out.

[PowermanKW]

Testing the effluent from your phosphate reactor with high grade test kit or photometer is one way you might be able to tell how fast to change the GFO out. You will have to test the effluent right after changing your GFO and then use this as a gage to make a decision as to when to change it out.

And I was going to do this till I thought my test kit was not very decisive. But that is an excellent way to see the differnce. I canged the GFO yesterday. I'll test tonight when I get home. Hopefully I will see a zero result, then I can monitor for punch through. Thanks for the reminder.

[PowermanKW]

OK, so get home, test the GFO effluent....comes out .02 mg/PO 3/4. OK great. Now I have a base line. Closest next to zero. So I said... let's make sure where my tank is at. I had done a couple tests before and they both came to .14

Well now my tank is at .02? So I tested DI water to get a zero reading.... not exactly zero... between zero and .02. So then I tested some tap water so I could see some phosphates....well looked like DI water. Less than the GFO effluent.

So now not sure what to think.... could my reactor actually clear my water from yesterday with a cup and a half of GFO????

[bertoni]

The time frame is believable, but I don't know how much phosphate 1 1/2 cups of media could remove. I personally wouldn't worry. It seems unlikely that the test kit is the issue, but you could get a second opinion if you're worried.

[PowermanKW]

Well I would certainly be happy. I tested just yesterday and it was .14. Changed out my carbon and threw in the GFO. I said before I was disappointed with the Merck kit, but now I'm pretty confident I was doing it wrong. Too bad I don't have a test solution. I will keep testing and see where I get.

[HighlandReefer]

Consistency in how you use the kits (whether they are off a bit of not) is the important thing. When using the phosphate kits like Merck, using proper procedures is a must. Keep the equipment clean with rodi water after use. Keeping your hands out of the equation. Keep the surface you use clean. Use the same lighting to interpret results (natural daylight bulbs are best). ;)

[PowermanKW]

Thanks for the tips. I am pretty anal about those sort of things. Clean everything with DI before and after. Don't touch anything. The only thing now is I have not done it in daylight the last couple of days, but I pretty confident with the differences even if they are not in the best light.

Sometimes I might have to do grab samples at the plant. No matter how well I do it... I always throw out the first test cause I don't think I did it good enough. The second one always comes out the same.;)

[HighlandReefer]

Keep us posted with your results. :)

Many other hobbyists may find your results interesting and helpful. ;)