Water Quality Tests?

Question

I have liquid and strips that I use, sometimes using both just to compare readings. In the case of my pH, my strips say it is at 6.4, whereas my liquid test says it's closer to 7.8. How can they be that different? I would take it to my pet store, but they use the same strips that I do.
My other concern is that last night, with the exception of my pH, everything was at zero. Ammonia, nitrate and nitrite. They had all been a little above zero, but that's expected since I had recently introduced a betta. Now they show they are all at zero, even the nitrate. I think I did something wrong in testing. Is it a good thing or a bad thing when they all drop to zero? Would it be safe to introduce another batch of fish, or should I wait a couple more days and continue to test the water?

My questions are:

1. What should I do about the wide range in difference in my pH readings?

2. How should I approach everything dropping to zero?

Details about tank listed in additional details...

55 gallon

350 BioWheel

Marineland heater

8 zebra danios

1 male betta

Mardell (??) test strips

API liquid test kit

Water changes every 3-4 days (20-30%)

Feedings at 8 A.M. and 8 P.M.

Anything else you need to know to assist me?

Thanks a bunch!

Answer 1

First, generally speaking the liquid tests are far more accurate than the strips. Strips are easily damaged by moisture and heat as well as light and just going out of date faster. Be sure you hold the bottles straight up and down for the liquid tests though, that affects the size of the drops and therefore the reading you get. So I would be inclined to go with the results of the liquid over the strips personally. Sounds like your strips are damaged or going bad to me.

Ammonia and nitrite readings of 0 are a good thing, that's what you want to see. It means your cycle is working perfectly. While your nitrates should be very low in your tank, nitrate readings of 0 are practically impossible, so I would blame that on a messed up test strip or an accident during testing.

Double check your tests before you add any more fish I would say, just to be sure.

I also wouldn't be concerned over the pH reading. 7.8 is fine for most fish and unless you have very sensitive fish it's better not to try to adjust it.

MM

Answer 2

1. Honestly, don't worry about PH. The fish are very tolerent of a wide range, and trying to adjust it tends to lead to unstable water. Those who keep it most simple tend to have the least problems.

2. Tests do expire - make sure they are all fresh. In a 55 gallon tank your stocking levels are very low, which means its not unreasonable for the nitrates to also be very low.