I am battling dinos right now in my 125g tank/30g sump that is 9 months old. I just had diatoms at first, then one day a jebao wp-40 went out while I was out of town and my tank was covered in brown snotty looking algae when I returned. After this happened, I bought a new RODI unit to switch from tap water (should have did this from the beginning). I started aggressively making water changes to get rid of the tap, even though my nitrates were <5, and phosphates were 0. Well that really set the algae off and at this time I realized it was dinos after searching for an answer... I have every symptom and photos are an exact match.
So far I have:
-Started dosing peroxide at 1ml/10 gallons, around 14ml total split into morning/night. I'm on day 5 of this.
-Did a complete blackout for 2 days. I lost two fish during this time, and almost a third so I had enough.
-Vaccumed sand bed and live rock using a small diameter tube rigged to the handle of my glass scrubbing tool, and a coral feeder (like a turkey baster) to blow the dino off the rocks then suck them up. I ran them through a filter sock with floss inside, then returned the water. I couldn't get them all but it made a dent it seems.
-Cut my skimmer off and stopped water changes, hoping to raise my nitrates.
So far the peroxide is helping, but not wiping them out yet. I'm running my lights for around 3-4 hours a day and some do reappear on the rocks during this time.
I've been reading about adding copepods, phytoplankton, and microalgae to help add diversity to the tank. My question is will the peroxide dosing kill the copepods if I add them soon, or should I wait until I'm finished (at least 2-5 more days).
I'm self employed and I hear you on the cost of things being a major factor. I'm waiting to borrow a microscope from someone, and if I find I do have Ostreopsis I may throw in the towel as well. 
Do have a peek to make sure you haven't had something die. Dinos are stinky but they don't small at all rotten to me.
