Nitrates were reading in the 50-60 ppm
range. It took 3 weeks of 20% water changes twice per week to get it down to 40 ppm
, and it's a struggle to get it to stay there.
It's a 20 gallon tank with 5 cory cats, a flower shrimp, 2 cherry shrimp, 2 otos, and 4 white clouds. That's a little more than the 1 inch per gallon rule, but the tank is also heavily planted, and I have two filters going - a HOB
biowheel, and an internal. The tank has been up for about 6 months, and even before I realized the nitrate problem, I was doing 20% water changes once a week.
The white sand is very fine - the kind that's almost like a powder. It's supposed to be better for the cories. You can't vacuum anywhere close to it, or it sucks right up with the water. But it's supposed to keep the tank cleaner than gravel because it compacts and doesn't leave any gaps where debris can sink down into it and decompose. And it's white, so I can see any debris that collects on top and pick it up with a net or a long spoon. But no, I don't vacuum up my substrate every couple of days, wash it out, and dump it back into the tank. I thought you weren't supposed to do that.
We went through a little patch of rainy weather a month or two ago, and the tap water always smells funky in L.A. when there's any rain. So maybe there was a lot of organic matter in the tap water from all the runoff, and my water changes weren't very effective because the nitrates were pretty high in the tap water to begin with.
I'm thinking about keeping the lights off for a few days to kill the algae, but will that mess up my water chemistry even more if I'm starving my plants of light?
How safe is it to do a 40-50% water change when you have shrimp? Are they sensitive to that?