Hi, Amy!
Things are good here - hope it is with you too!
I always fed about every other day... for pretty much everything except Anthias, then daily feedings of small amounts.
Where are you hearing that garlic is bad? Generally, I'd agree that terrestrial foods aren't necessarily good, since they wouldn't find them in the wild, but the garlic is used as an additive, not as the main part of the food, and so many manufacturers are using it or making supplements with it, I can't see it being bad. We used it routinely.
So you're feeding more than "average", and you aren't vacuuming the substrate. Food, whether it's eaten or not, ends up in the sand/rock... either as leftovers or somebody's poop, whether it's fish, coral poop or invert poop... and what goes up, must come down so while the filter catches some, plenty ends up in the substrate or rocks.
It's not being cleaned up (ie vacuumed)...stirring into the water column allows a filter to catch some... but what happens to the rest? Refer back to the law of gravity.
Yes, beneficial bacteria break some of it down... but "everybody poops"... so even if it's broken down further, it always comes back to poop (!).
So by vacuuming the substrate - you may be surprised at how much solid waste is hidden in the sand. Fan up the detritus off the rocks - some will settle back on rock and some into the sand where you can vacuum it... or if you break the tank down to scrub again, make sure you give those rocks a good swirly in the bucket of waste water to dislodge the crud and shed it into the waste water.
It's not a perfect technique - you're never going to get all of it (and more is generated daily)... but getting most of it will cut the algae's food source somewhat.
There's nothing wrong with feeding generously - as long as the amount of cleanup is equal to or more than the amount of waste being produced.
Picture the waste as if it was trash. The fish eat, poop, maybe some food is left uneaten. It's litter dispersed all over the tank. Beneficial bacteria sort that trash, and some of it they can recycle, and the rest is left there for you to take out, by vacuuming and changing water (because some waste is dissolved, and some is not).
You're giving the fish enough food to generate 3 bags of trash per week. The bacteria process, say, one bag. That leaves 2 bags for you to take out to the curb. Thing is, you're only picking up one bag. At first, that spare bag is no biggie... but then the next week, there are 2 bags left, then 3... before too long the house looks like something out of, "Hoarders".
Typically excess waste can show up as high levels of phosphate and nitrate... but in your case (and many others' cases), algae grow and they use up those nutrients like fertilizer on your lawn. So water looks clear, tests come out within acceptable ranges, but the forest of algae becomes such a nuisance... The algae are unsightly but they're actually doing you a favour.
So the answer is to cut back on garbage in and/or increase garbage out. Want to keep feeding a lot? OK... but you'll need to step up water changes to keep up.
Hopefully the visual analogy of the 'trash' is helpful in understanding what's going on.
Using the same visual... it's better to do small water changes more frequently, than larger ones at larger intervals. It's better to take out a small bag of trash every day (or few days, etc.), than to let it build up in the house, and then take a huge, smelly load of trash out once every 2 weeks or so.
Jenn
