That helps...so its a HOB (hang on back) powerfilter, tetra whisper. Not a bad filter. If you invested in a canister filter, or a 2nd filter it'd probably help a bit, but honestly there isn't any magical fix. You need fewer fish or a bigger tank. Tanks are not cheap...but you could try something like
www.craigslist.com and keep an eye out for a 90G setup for a hugely discounted price? If a larger tank is totally out of the question you might think about putting an ad ON craigslist for your community looking for a good home for like half of your fish or something? I'm sure others will have some input for you too.