Foreign objects in tank, fish growth, etc.

Question
Hi, I set my tank up last july (2004) and it is a 20 gallon tank. I have 3 black neon tetras, 2 grape tetras, one spotted cory, some pond snails, and 2 goldfish (I know you aren't supposed to mix tetras and goldfish, but I didn't know that at the time I bought them and they have lived peacefully together since I got the tank in July). I have an under gravel filter system and I have no idea what the ammonia and nitrite levels are, I think the pH is about 6.8 but I'm not sure.   I have a few questions to ask you.  First, I've noticed this cream-colored flaky looking stuff in my tank attached to my heater, I was wondering what this was, I touched some of it and it was rough and hard, I don't really know if it's harmful or not.  Also, I was just wondering how long it takes a corydora to grow to full size. Lastly, if I got one of those big snails (not pond snails, ones that are like 2 in.) what are you supposed to feed it?  I read that you are supposed to feed it blanched lettuce leaves, but will it find it before my other fish do?  Thank you for your time.
Leah

Answer
Hi Leah;

I won't give you a hard time about your combo of fish. It is pretty wacky though! Lol! I'm glad they seem to get along okay.

The crusty stuff on your heater is just minerals from your water. The heat makes it collect there. Just wipe it off. It isn't harmful to the fish.

For great info on Apple Snails or "Mystery Snails", here is a site to go to;

http://www.applesnail.net/

It should tell you everything you need to know about them. They're just not my specialty.

Have fun with those guys!

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At Your Service;
Chris Robbins

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