Weird big insect

Question
The tank's been set up for about 4 months. I'm not sure I think it may be 60 gallons. We have 3 adult female guppies and one male. We also have one plecko. There are a lot of guppy fry. Some are quite new, but some are starting to get colour on their tails. There are many small snails as well. We have about 4 plants. I don't know what kind of filter. I don't know the PH. I don't know how often my husband changes the water.

Tonight my husband pointed out a smallish brown black object on one of the plants. He saw legs. Sure enough we could see it had 6 legs when he scared it onto the pebbles. It looks (not to be crude) like a small animal dropping. I'd guess it's about 1 to 2 cm long. My husband isolated it because we're pretty sure it's feeding on the fry. It's legs looked striped but it's body is lumpy. It doesn't look like a toe biter, but what could it be? Most sites don't list big insects as common pests.

Answer
Hi Tracey;

It could be a Dragonfly Larvae or the larvae of the Predaceous Diving Beetle. They both have six legs and eat small fish so your little guys could be in danger. Their eggs, or even the creature itself, may have come in with live plants. Here are a couple of web pages with pictures of those and other types of water bugs you can compare to yours;

http://www.weloveteaching.com/hopepond/macrobug/macrobug.htm

http://www.microcosmos.nl/maingal.htm

At Your Service;
Chris Robbins