We have had our Betta fish, Sam, for about 2 1/2 wks. We have a 2.5 gallon tank with a heater, filter, thermometer, two fake plants and a cave/tunnel. I've been doing a 50% water change every other day to keep the ammonia at 0. The Ph was ~7.2 earlier today. I use water test kits for those. I have test strips for the nitrate, nitrite, etc. and those all seem to be okay too.
Yesterday, the water started looking dingy. Not cloudy, but dirty. I did a 50% water change, but it still looked that way today. I changed the filter, although it didn't look dirty. After a few hours of no change, I put the drops of stuff that is made to clear up the water. It said it causes the particles to get stuck together so the filter can get them. Still no change though.
I also noticed on some of the shiny rocks it looks like there are black specks all over them.
I'm not sure what to do now to fix it. Any advice would be great!!