Fellow fish nerds, I need some help. Just lost two fish in two days and need to know how to move forward. Here's my current situation: TANK A few months ago, I upgraded to a 75G. I was running a 20G long for about a year with no issues. Moved livestock over from 20G (Pair of clowns, fire fish, fire shrimp). Added more live rock (about 45 pounds and 60 pounds of sand). Just started to recently get an outbreak of brown algae, figuring that my tank had a minor cycle to possibly do because of all the new space with my older items in it. Added a Flame Angel, Kole Tang and sea egg over the two month period of the new setup. No sump (yet), have CoralLife 125G HOB protein skimmer. Parameters and Personality I do water changes religiously. Everyone is happy in my tank and gets along great. Stress shouldn't have been an issue. My Kole Tang and Flame Angel were best friends they hung out so much. My tank just had a slight ammonia spike (0.25 ppm), nitrates have been hanging around at a steady 20 ppm and my nitrite is 0. I've been using a nitrate reducer from the LFS to help with this, but I'm wondering if I need to add more live rock or if a sump will do the trick. I can't imagine adding more rock to the tank because it'll just dominate it. I also only feed my fish every other day to eliminate any overfeeding and make sure it's food they can consume within three minutes. Kole Tang Ich I didn't see it at the time but the Kole Tang had a spot on it's lower fin once I added it into my DT. It blossomed, and eventually gave my Flame Angel ich as well, even though it wasn't nearly as serious as it was on the tang. I pulled the Kole out of my tank and put it in my old tank that I set up for a QT. I took water from my DT, used an HOB filter without any carbon and put some PVC in there for it to hide. I was dosing the water with Kich-Ich, a non-copper Ich medicine that is safe for all inverts and fish, either scaled or scale-less. The Kole Tang died three days later in my QT. Flame Angel Death This morning, I woke up and the Flame Angel was stuck to the intake of my HOB protein skimmer. I freed it, but it swam all sorts of ways and just sank to the bottom gasping for air. Due to the stress, it had more ich on it, but by judging from how it was acting in my tank previously, I blame more of the death on the protein skimmer than I do Ich. Moving Forward I'm getting ready to go to Petco and take advantage of their $1 per gallon sale. I'm going to buy a 20-29 gallon tank depending on what fits under my stand and look at how to make a homemade sump. I will also be quarantining all of my fish. QUESTIONS!!!! QT Tank: What recommendations would you make? I could permanently set it up, but I'd rather not have to maintain two tanks. I could set it up on an as needed basis, but would I always copper dose my fish for the two weeks or so of watching them? Do I have to do a full water change before every new fish? Is it fine that the tank isn't cycled? Should I just add water from my DT, even though Ich is technically living in it? Treating DT: Should I use the Kich-Ich in my DT tank? I would prefer to not harm my Fire Shrimp and Sea Egg so I'm very cautious about adding ich medications. Should I add a JawFish to help clean the sand of brown algae? I've attached a picture of my tank as well.