Come to think of it, I do get quite a bit of gunk when vacuuming the gravel. Same gunk inside the canister. A light brown film also forms on the inside of my return/supply hoses a couple weeks after I clean them. It's a flaky substance, like shrimp poop or tiny particles of decayed plant material. However, all my plants appear to be healthy. Although I do have some algae on the lower leaves of my golden jenny. I've been dosing 10mL of Excel daily to keep it under control (as advised my another member on this forum). I don't have any algae growing in the glass. Just a little diatom growth along the the bottom edge where the substrate is. I clean the canister at least once every two weeks and am always surprised by how filthy the filter floss is, which I toss out. It's only a 20 gallon tank, so it isn't as forgiving of any fluctuations. I'll give the tank and canister a good cleaning, do a 60% WC, then forego the KN03 next round I guess.
1/8 tsp three times a week, just like the table says.
OK I don't know what table you mean, but with three doses that is about 15 ppm weekly. So with 50% weekly water change that means about 30 ppm accumulation plus fish load minus plant uptake.
How are you measuring NO3? API kit?
If so, I would not be convinced it is correct. It is well known to be off quite a bit. If you really want to be sure, you can make a calibrated solution (directions in the shared drive in my sig).
If you are somewhere right about 40 ppm NO3, it's really difficult with the API to distinguish between 40 and 80 ppm. It helps if you dilute your sample. Mix the 5 ml sample from the tank with 5 ml of tap water (assuming it has no nitrates...I use RO or distilled). Then use 5 ml from that 10 ml of water and test again. You might find that reads about 20 ppm, which would put you at 40 ppm. That's actually about right for most EI dosed tanks.
And in general, how are the plants doing? They look pretty good in the picture. If so, I would not be worrying too much about the measured level, and concentrate on the dosed level and the response of the plants.
I meant the table on the sticker that came affixed to the KN03 fert container (GLA). It says 1/8tsp KNO3 three times a week for 10 to 20 gallon.
Yes, API. Nearly impossible to distinguish between 40ppm and 80ppm. I'll do the dilute test now and post back.
Okay, I did a 50% diluted and a 75% diluted sample. Based on the two samples, I believe my nitrate is closer to 60ppm. The test instructions say to hold the tube against the white area of the card, but in doing so, the second sample appeared to read in the 20s, so I don't think that is accurate. I held it up alongside and it looks more like 15ppm or so, which would give me 60ppm (1:4 ratio). Regardless, it's way too high.
Crap, I just tested my other two tanks and the nitrate is above 40 in those as well, and I don't EI dose them, just an all-in-one liquid fert twice a week. Guess I could be over feeding, but the fish eat what I give them in under a minute. They go nuts.
This is what the water out of the canister always looks like when I clean it every two weeks. And this is without wringing out the filters. I simply removed the media and dumped the water into the pitcher. It appears to be dead plant matter, but I don't have any dead or dying plants. Could it be due to me adding Excel every day? I.e., the excel is killing algae and it's ending up in my filter, which is why it appears I don't have an algae problem?
Attached is a pic of the gunk and here's a video: