Hi,I setup my new aquarium 2.5 months ago and I noticed a strange creature 4 weeks ago that looked like a small spider in the gravel. Last night that creature reappeared and is considerably bigger and no one seems to know what it is. I have been losing 1 fish per week, even though testing shows my water to be fine PH 7.2, Ammonia 0, Nitrite 0, Nitrate 40. I have 6 neon tetras, 5 white tip tetras, 1 catfish and 2 guppies. You'll see what plants from the picture. Over the last 4 weeks I have lost 2 gouramis and a few neon tetras. The creature was not seen at all for 4 weeks, it is an inch long now. Are you able to help?