I've had a 10 gallon stocked with 5 black skirt tetras for well over 8 months now. 2 of those tetras have been in the established tank for 16+ months. Over the past two months I have noticed that the tetras all hide a lot under the decorative plants and petrified wood setup. I first thought it was due to the lighting because I didn't have a regular schedule setup for having the lights on - they usually hide when lights are on. But, lately it seems they hide all of the time and I hardly notice any activity from all 5 except during feeding time. I feed just standard flakes once a day and have been doing 50% water changes once a week. The water changes used to make them a little more active for that first day or two, but the last one didn't seem to make a difference. Last time I had all of my water parameters everything checked out ok and the pH was 7.6. Few questions.... I did a few searches and found some mixed results. I will try the water change but it doesn't seem to be a perma solution. Could it be parasite related? Could it be that the standard 10 gallon filter that came with the tank (Whisper) is just weak? Thanks in advance.