free swimming things in my aquarium

Question
I have a 10gal tank full of guppies. I just noticed these small semi clear dots swimming in my tank. Under the microscope they appear to be round and covered in hair (reminds me of a flea but it has a hard ectoskeletin and they are full of eggs. I just added tap water to the tank about 2 days ago and now I have these things all over my tank.

Answer
Hi Tracie;

They are probably daphnia, rotifers or some other harmless pond critter. You can do an internet search using those names and see what comes up. If they are not attaching to your fish they really aren't something to worry about. The fish should actually be eating them. If you cut back on food a bit they will get a little hungry and probably gobble them up. Adding tap water probably just stirred them up a bit and now you can see them more. There may be something naturally occurring in your water that they really like too so they became more active when they got more of whatever it is. I wouldn't worry unless your fish are having symptoms of problems. If the fish seem sick, make a 25% water change and vacuum the gravel to reduce the numbers of the critters as well as remove waste. Let me know if you have more questions...  

At Your Service;
Chris Robbins