So I have this Eheim 2224 used for maybe 3 months. I dont know what to do with it.
1. Use it on my 10 gallon CRS tank
2. Use it on my 20 gallon quarentine/breeding tank
3. Sell/trade it
4. Save it for a rainy day
You'll probably end up losing a little bit on sale, trade wouldn't be bad, but I'd say save it, you never know when you may find a use for it or some pieces of it, and you can use it on either of your first two options until you find something better.
Keep it, you never know when MTS will get you and want to setup another tank. I've setup like 4 tanks just on extra stuff laying around lately for my roomates. When you have filter, lights, substrate and all you need is a tank, thats the cheap part. lol.