angel treatment

For the past few weeks I have been treating my angelfish for suspected external parasites.

She gets unsettled when the water is so low-

I've noticed for a while that she will get twitchy, or jerk and dart across the tank. Then this behavior- she'd hold herself still in the middle of the water column, head pointed up, and a guppy would pick at her sides, until she jerked and swam off. I saw this with my paradise fish before when it was unwell- I thought the guppy was picking at fungus on its side but now I think it was cleaning off parasites. I was still unsure though but then three weeks ago Miss Beautiful started to go off her food. Would take bites and spit them out, or not show any interest at all. 

First round I did a normal water change (being rather short on time that day) and dosed with Prazipro. Angelfish quit being as twitchy and started eating again in the middle of that week. Five days later I did a large water change and dosed again. Seven days after that saw her acting twitchy again so repeated the large water change and Prazipro. By large I mean changing out almost thirty gallons instead of the usual thirteen or fourteen. I brought my two and three-gallon watering cans into the room and filled them straight from the tank as part of that:

I used my acrylic tube like a long straw, with finger on one end, to spot-clean in crevices and under/behind the hornwort stems, where it's difficult to get with the regular siphon. And did extra rinse of the filter sponges. Plus I've been feeding the fishes garlic-soaked micro pellets once or twice a week- but Miss Beautiful doesn't like and spits them out. The guppies and kuhli loaches eat 'em up, however (and they've shown no signs of illness). 

Would really like to get rid of this issue, hasn't my angelfish been through enough. I'd also really like to get a new paradise fish or betta, but all the small items I'd use for a quarantine tank are in the back of this tank, so pulling that while it's infected with parasites not a good idea.