Nitrate and Phosphate reading zero but I have algae...

lastlight

Premium Member
My tank is just over 200 gallons and I keep things basic. Skimmer, 45g water changes usually every 3-4 weeks and moderate use of gfo and carbon (though I should replace more often). I feel like my corals are looking quite washed out and generally could look better. Haven't had polyp extension nearly as good as some of my past tanks.

I'll be honest and say I don't ever really measure Phosphates or Nitrates. I bought a Hanna meter and an Aqua Forest Nitrate kit when I was going to dose NoPox but I had tried dosing once and things didn't react well. Fast forward about a year and I was going to give it another shot since I get film algae back within 24 hrs and it's really annoying. I really don't have any algae on my rocks other than coraline. Now the reason I see my Hanna as a giant waste of money is that EVERY time I ever do a test it reads zero. And apparently my algae might be using the Phosphates too quickly to detect it? That's always baffled me. And the Nitrate kits are always matching a colour so my zero readings seem untrustworthy as well.

My question is, could my levels really be zero? I have two tangs, 7 chromis, 2 anthias and 2 blennies. Pretty light load I guess? I feed some NLS, cube of mysis and some nori pellets everyday. I think the Phosphates likely aren't zero but could my nitrates be zero? From what I understand I can't use the NoPox to strip phosphates if Nitrates are already zero. Maybe this is why that experiment didn't work so well last time.

Any ideas on how to proceed? I could just up my replacement frequency with the GFO assuming I have phosphates since the film grows back so fast. But zero Nitrates aren't good.
 

bertoni

Premium Member
The levels likely are close to zero. Algae can consume mineralized nutrients fairly rapidly. Some people have good luck with GFO outcompeting algae for nutrients. I'd try that first, since it's easy and inexpensive. Other people prefer vinegar or vodka dosing, and they are reasonable, too.

Some herbivorous snails might be able to keep up with the growth, though. Trochus and Stomatella seemed reasonable to me. They can reproduce in our tanks, which is handy.
 

lastlight

Premium Member
Thanks for the reply. So you don't think I need to try to raise my nitrates so the test shows a tiny bit of color?
 

bertoni

Premium Member
People are successful with a wide range of approaches. Personally, I would try a bit of GFO first, but controlling algae can require trying a variety of techniques to find one that works for your tank.
 

lastlight

Premium Member
Yes I'll certainly change the GFO more frequently and see how that goes. I've got no algae problems anywhere but on the glass. It's just annoying to lose a clear view into the tank after a day. I'm more concerned about the low nitrates. Should I have measurable nitrates and should I try to add any? In nearly all of my tanks I've found my sps to look more pastel/pale coujd this be the cause? Thx.
 

bertoni

Premium Member
Hmm, if the corals look a bit pale, dosing a bit of nitrate might help, but coral coloration seems to be a complicated issue.
 

lastlight

Premium Member
Thanks. I'm reading up about dosing nitrates and how that generally leads to a reduction in phosphates. I'm hesitant to mess with that since I can't seem to get readings of anything besides zero on my Hanna checker and might not be able to tell what my levels really are. Before getting into a N03 P04 dosing pattern I will try heavier feedings and see what happens.
 

coralcruze2020

New member
Algae is consuming the nutrients in the water column faster than test kits are able to detect them. it takes time for high nutrients to work through the system and get lowered. Live rock can leach nutrients also.
 
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