Choosing a filter, heater and hood. Help please.

[Defence21]

Okay, so now that I have my 10 gal. tank filled with water/dechlorinated, my next step is getting a filter, heater and hood. Keep in mind that the reason I am doing this in pieces is the money factor. I'm just getting what I can, when I can.

So anyway, I went to the local stores and did some research on prices and available supplies. I found that filters range in price pretty drastically and I was told that getting a filter that can go up to 20 gals. might be a good idea. Here is what I have found:

1a. Whisper Power Filter 10 (up to 10 gal)
1b. Whisper Power Filter 20 (up to 20 gal)
1c. Whisper Power Filter (20-40 gal)
2a. Penguin Bio-Wheel (up to 10 gal)
2b. Penguin Bio-Wheel (up to 20 gal)
3. Aqua Clear (up to 20 gal)
4. Aqua-Tech (10-20 gal)
5. Cascade (up to 20 gal)

As for hoods, I discovered that there are 2 kinds of lights. What is best for tetras, platiess, guppies, killifish, rasboras, danios, etc? Is it fluorescent or iridescent?

Next, what about a heater? How important is this? I remember having tanks roughly 10 years ago and never had heaters and my fish lived for over a year. If it is a must, what is the best kind to buy? Keep in mind that I am on a tight budget, yet I still want to try to find the best I can while not spending a fortune.

Lastly, I noticed in 2 of the local fish stores that there are foam inserts for fish tanks that are hand-carved and painted to resemble rocks. They cover the floor of the tank as well as the back wall. Basically, it gives the tank a rocky look. It's unlikely that I will get one, as I think it would take up too much space in a 10 gal. tank, but if I were to gain an interest, how safe would this be for my fish? I just can't see how having foam submersed in water can be a good thing.

Thanks again for the help. I really appreciate the prompt responses you all have given me so far. Its nice to have a place like this to ask questions!

Matt