3 week old new tank, pH 7.8, soft & cloudy water

Oh my... that's a lot of fish for a new 10 gallon. Unfortunately, it sounds like you have received the same bad advice that I did when I set up my first tank.

First of all- stop using pH adjusters. These products will cause pH to swing, and this is very stressful for your fish. A stable pH is better than striving to get it in the perfect range. 7.8 is not really that high, and most freshwater fish are perfectly able to adapt. Just use dechlorinated tap water and your fish will be fine.

Second of all- any detectable level of ammonia is stressful, as it is extremely toxic to fish. Same goes for nitrite. Unfortunately, your tank is not yet cycled, so your fish will have to survive both an ammonia spike and a nitrite spike. If you don't have a test kit, I'd suggest buying one since it is the only way you will know where you are in the cycling process. A good test kit (use one with liquid reagents, like API, but stay away from test strips- they are very inaccurate) will tell you when you need to change water. You'll need to change enough water to keep ammonia and nitrite under .25, and you may have to do large water changes every day until the tank cycles. Do not vac the gravel or clean the filter until the tank is cycled (ammonia and nitrite is consistently at zero, and nitrate is detectable). Cut down on your feedings to once every other day. I promise, your fish will not starve, even though they will act like it. This will help your fish to produce less waste, and in turn will help keep ammonia and nitrite as low as possible. Once the tank cycles, you can feed your fish once a day, and do a water change once a week.

The bubble wall may be getting air into your filter. That could be why it is running so loud.

Agreed, don't mess with the ph. Really hard of the fish. They'll adapt fine. I'd do 50% water changes with dechlor every day until your tank cycles. Less food would be better. Just makes them poop more which pushes the ammonia and ites up. No fun there. Oh, could be the bubbles getting into you filter that's making it noisey. Try moving or even shutting it off for a minute and see if it quiets down. That will answer the question for sure. Hang in there, it's gonna be fine.

the bubbles could be getting sucked into the intake, which can cause noise. try moving the air stone to the other end of the tank.

Ditto on what everyone else said, and I'd like to add that distilled water is a bad idea unless you have a good reason to do it. (keeping sensitive fish, saltwater tank). It will not make the water less soft, it will make it more soft. Because distilled water has very little in it besides water, it is very soft.

Cloudy water is pretty normal in a new tank, it should clear up.