Should I Clean My Tank Befor Or After...

[fry_forever!]

Hi, a couple days ago, I posted a topic about my filter malfunctioning in my 4 year old 20 gallon tank. The filter was an aquaclear 30, and was over-heating and had barely any waterflow coming out of it, even though it wasn't plugged up. I got a new filter, according to recommendations, but now what should I do? It's time for my weekly water change, but should I do the water change? I don't want the ammonia to spike if I do a water change and then put the filter in. But if I don't do the water change, the ammonia will go up anyway, even with the help from the new filter, because my tank will be dirty for 2 weeks. What should I do? Clean before or after I install the new filter? I'm also putting my old filter cartridges into the new filter, by the way.

And with the old filter -- I'll probably get another 10 gallon and use the filter for that. The flow will be just light enough to support life in a 10 gallon. And the over-heating problem's not THAT terrible...

Thanks in advance for any help!

-fry_forever!