Is my pleco sick/dying?

Question
I have a 10 gallon tank with 6 danios and 1 pleco (about 3 inches long). It's been set up for about 8 months. I feed the fish both flakes and brine shrimp. Water changes I do about 25% every two weeks (this is what the fish store told me to do, although the water still seems to get greenish pretty fast-is that normal if all the levels are good?). No ammonia or nitrites, and nitrates are about 20-40. I haven't added more fish/decorations/gravel since I started the tank.

The problem is that about 1 week ago I noticed that my pleco wasn't moving as much, usually he zooms around every now and then and I won't know where he is in the tank. I just watched and waited since I thought maybe it was my not noticing when he moves. But then a few days ago, I noticed he was trying to attach to the side of the tank to eat some algae, but couldn't get attached. He ended up half on his back about an inch from the glass, propped up by a decoration. I noticed from this vantage point that he was breathing okay (I think), and nothing looked abnormal on his underside compared to what I would notice when he usually attaches to the glass. I didn't want to move him in case that would stress him out. The next day I found him in the exact same position. I went to the fish store to ask about it, and they recommended I add aquarium salt. I did that per the label. That day I decided to gently move the decoration and use that to tip him right-side up so that he could at least get algae from the rocks to eat. It's been about 2 days and the only movement he's made is to scoot about 1-2 inches farther into the corner of the tank. I can't tell if he's breathing well because of his position, but he only moves his tail the slightest bit every now and then. Please help!

Answer
Hi Nickole
Is there enough algae in the tank for him?  Plecos are pretty good at getting rid of algae fairly quick.  Do you supplement his diet at all with algae wafers or veggies?  Try putting a piece of lettuce, zucchini, cucumber in the tank, a veggie clip works best, but you can anchor it down under a rock or decoration.  See if he eats that.

Plecos are sensitive to salt, so I'd recommend doing a partial water change to remove some of that.  And, I'd up your water changes to 25% once a week instead of every 2 weeks.  Your water parameters look great, nitrates are ok but ideally you want to try to keep them under 20 ppm.  I think doing the water changes weekly will help that.  

I really don't know what, if anything is wrong with him at this point.  It is common for plecos to starve, like I said, they do clean all the algae up fairly quickly in a tank.  He may just be showing signs of starvation.  See if adding the veggies helps.  If not, let me know, and also let me know if any other signs or symptoms show up.

Christy

Usually plecos are more of a nocturnal fish.  Try watching him at night when the lights are off, see if he's more active then.  Is there any other symptoms he's showing?  Does his belly look sunken in or swollen out?  Any red spots?