Quite a bit to update
Why not put a reducer at the end?
What would a reducer do? It would put backpressure on the durso standpipe and would cause the 'toilet flush' noise. Even just putting the 1.25" ID tubing onto a 1" ID barb and converting it to FlexPVC caused enough backpressure to cause the toilet flush.
Ok, for a list of changes made to the system.
Tunzes are gone. I've now got two Vortech MP40wES and one blue box MP10, but today I got the wES driver to sync the MP10. One of the wet sides on the Mp40s was about toast when I got it, so I bought another from a member here, which that one was I guess only used for a short while, but it was basically toast, too, but between the two toast ones I got one wet side that was kinda working, so I ordered the parts to fix it and those came in today, also.
I took the algae scrubber offline yesterday. I guess I am now in the algae scrubber cursed group, I can't get anything to grow on it besides a bit of bryopsis, and that just won't do. I tried everything - increased light schedule, decreased, increased total light, decreased total light, quadrupled flow, even, to no avail.
I got a new skimmer, should be here next Monday. It's a Reef Octopus model, but instead of the OTP pump, it comes with a Bubble Blaster HY-3000, essentially turning it into an SRO-2000.
Lighting is changed again, this time to a custom LED/T5 hybrid. See my thread in the lighting forum for details on that.
All of that being done, I can't wait to sit back and stop touching this tank. I've gotta pull the fish out once and for all and treat them for ich, I've been fighting this strain for so long now, it's ridiculous. I'm trying now to secure chloroquine phosphate to treat with instead of Cupramine, I think it may be resistant to copper. I got an order from LiveAquaria last week, and out of six fish, I have one survivor, but at least two were lost from shipping stress. So i essentially paid $65 for a coral beauty angel.
I added three acan frags last Friday that are looking good so far. I didn't realize how fresh of a cut they were (less than 24 hours, grrr) but are surprisingly well so far, open and fluffy and reacting to amino acids with feeder tentacle extension.
I lost a bit more of my remaining coral, all my euphyllias and a few other small pieces, some of which I don't even remember what they were. Oy. One of the euphyllias was my first coral ever

At this point, I have no clue why I lost them, realistically. My alk was higher than normal, but other than that, now I'm doing more things 'correctly' (like having a 'proper' amount of light and flow, good skimming, temperature and pH monitored and within normal ranges, using RO/DI water for topoff instead of just RO, etc etc), but having less success. I hope this passes.
Current pic of the system: