Crap, I just lost my entire huge post! grrrrrrrr
Anyway, I'll type it all again:
Wow, like the posters above said, that's a HUGE amount of fish for such a small tank! When you said you had 17 fish, I thought you meant they were babies. I had 12 large goldfish once, and they were in a 125 gallon tank! 72" x 18" x 23" (473L = 184cm x 47cm x 59cm)
Since the cloudiness isn't green, it's not "green water" algae. Since it's white, it's free floating bacteria that are feeding on excess wastes not being processed by your filtration. I'll bet anything that you have lots of ammonia in your water, if not nitrite, too.
First, if you don't already have a testing kit, get one as soon as possible. You need a liquid kit that tests for ammonia, nitrite, nitrate, and pH, minimum. Once you know the results, post them here. Here's one kit that I recommend: API Freshwater Master Test Kit
Second, your fish are quite fat, so you are probably overfeeding them. You should cut down feeding to reduce wastes. A goldfish only needs a pellet the size of their eyeball once or twice a day. It'll slow down their growth, too, until you get that bigger tank you said you're going to set up.
Feeding pellets will help you keep track of how much you're feeding. Here's an example: Hikari Goldfish Diets.
They should probably be eating something the size of the "Hikari Staple Mini Pellet." If you have 17 fish, I'd feed 20 pellets once a day.
Third, it won't hurt to change 50% of your water twice a week, at least until we figure out what's exactly
wrong. If we can't fix some of the problems, you may have to continually change much more water than you are now, until the large tank is set up. Clean water = healthy fish!
Fourth, you said you changed out the gravel. The bacteria live not just in the gravel but on all surfaces in the tank, so you lost some of your bacteria. Oh, well, what's done is done. Now to care for your gravel: if you don't already have one, you should get a gravel vacuum. It's a siphon with one large end that you plunge into the gravel all over the tank. As it sucks out water, it sucks the waste out of the gravel. That will greatly decrease the waste load on your filtration. Here are some examples:
Python is the best brand! The second is the best kind, since it attaches to your sink faucet and requires no buckets. You'll also need it for the big tank, anyway.
Fifth, you said that you're using two filters. What exact model(s)
of "Boyu" filters are you using? Knowing this will help us determine if you have enough filtration for your waste load.
What kind of media is inside the filter? The way the instructions say to set it up is not always the way to get the most biological filtration out of it. Most of the new Asian export filters now coming to American and European markets like these are well-known to have horrible instructions. :/
What filter maintenance schedule are you keeping? You shouldn't need to clean each filter more than once every two months, ideally, and you should only do one filter per month, so you don't lose too many bacteria all at once. But if the filters get clogged very easily, that may not be possible. We have lots and lots of ways to solve these problems.
The manufacturer's web site is here, but it should say what model on the filter itself: Boyu USA
That's all I can think of for now. If I have any more questions, I'll add them later. It's important to have honest and thorough answers to all
the questions I asked! Cloudy water may be just the first symptom of a big problem starting in the tank, often called a "crash."