Nitrates

[aquak]

I've never paid much attention to nitrates until now when I have a 70 gallon tank that has more algae than I'm comfortable with. I tested for nitrates to see if that was the problem and the reading was 0! Next I checked my 30 gallon that doesn't have an algae problem and the reading was 160! Does this make sense? I did an overdue water change in the 30 and it went down a bit, but I wonder if it's really a problem since all else seems to be OK. Should I keep doing water changes on a daily basis? I've gotten the algae down a lot in the 70 by limiting the light. I also just added 3 otocinclus (otocincli?) and more plants, and the royal pleco eats some, but should I be doing anything else? All my tanks get about the same amount of sunlight. The 10 gallon (which had fish, but doesn't now) actually gets the most and has no algae, the 30 has enough for the otos, and the 70 has too much.

[AngelMom]

If I remember correctly, your 70 gallon is fairly new isn't it? Just wondering if that is part of the issue with the algae as I had a pretty bad bout with algae in my 60 gallon about 2 months after it was cycled.

Have you checked the phosphate levels in the water? That has been about half of my battle with algae in both my 60 and 55 gallon tanks. The first time I bothered to check the phosphates in the 55, they were over 3 ppm (should be no more than 0.5 with 0.2 being optimum). Between controlling the phosphates (using filter inserts) and adjusting the lighting, I've been able to completely minimize it in the 60 gallon and am starting to get it under control in the 55 gallon - the lights in the 55 are a higher wattage, so I've had to reduce the time they are on. The pearl gouramis apparently like this aglae and are helping to keep it off the plants (at least SOMETHING is going right!)

As for the nitrAtes, I know you have plants.....are both tanks heavily planted? I'd think the plants would use more of it in the 30 gallon if it is. The algae is probably using whatever available nitrAtes there are after the plants in your 70.

[aquak]

That's why I'm wondering why the 30 has no algae problem and the 70 does. Yes, it's fairly newly set up. I was going to test for phosphates but, when I saw the test cost $17, I decided to start with testing the nitrAtes. I might take a sample to the store and let them test it for me, but it'll be a while till I get back there. I still don't understand why the 30 has such high nitrAtes. Do I need to worry about it? Maybe I'll put a big wad of java moss that's now in the 10 back into the 30.

[AngelMom]

160 is a bit high. I've seen recommendations to keep it between 10 and 40 ppm where possible and under 80 ppm for sure, but saw somewhere that the nitrAtes don't reach toxic levels until about 200 ppm. Suspect no one knows for sure, but I try and keep mine as low as possible and below 40 if I can (so far so good!)

[AngelMom]

I realized there is another possibility (of course, it was AFTER I shut the computer down last night). Do you use any fertilizer for your plants? Anything with nitrogen in it may show up as nitrAtes in your test.