75G Mixed Reef Sudden CRASHING?

[Flare]

Hello, I am a pretty new reefer, moved tanks in March and this system was thriving with the cycled rock and water, and now my tank crashed and has been withering away over the last week. All zoa polyps closed, xenia died back and shedding, kenya trees dying, birdsnest and monti dead, mushrooms shriveled, my GSP and Duncans are the only ones still slightly opening. Lots of brown algae has appeared, keep cleaning with a brush but it keeps coming back. My water has also become slightly cloudy and im suspecting its an algae bloom. As soon as I noticed all polyps closed and the monti + birdsnest dead, I cleaned my tank, brushed the rocks and removed some bubble algae, cleaned the sand a bit, and then I did a 15g water change, then cleaned the canister filter and put new media. The water change however raised my KH by like TWO! Now im stressing even more :) Today I woke up to my cleaner shrimp dead, and noticing my snails are kinda not moving or are on the sand and not rock or wall like usual.

My Practice: Previously, I hadnt been doing water changes because my water was super clean, so id been dosing Nitrogen to get and keep my nitrates above 10ppm, and I had a KH around 7 and PH midday at around 7.8. I had some Marine Buffer new that I got for free, and used it once a week to see my ph higher and get my kh to 8. I also dose Calcium. Every Saturday I dose Phyto Plankton and Sundays I dose ZooPlankton. I feed brine shrimp flakes, pellets, and marine cuisine once every 4-5 days. I dose reef roids every two weeks-ish to keep my phos above 0 (without the media my phos would get too high). Fish do not pick at corals.

My Thought: Admittedly, Finals week just passed and I neglected dosing/ordering new nitrogen for like two weeks. Thats when I noticed the crash, my Nitrates went from ~15ppm to ~6ppm. Everything else was fine! Only other change I made was getting the Nicrew Light Controller, to have a ramp up and ramp down time, but I kept the same settings and height. LFS said I might have a hotspot, so I bought a par tester and checked my tank, and everything was under ~230 par. I went ahead and decreased my lights a bit to get it down to softies gettings under ~190par. Turned off the Red spectrum and decreased the Green, White is at 10% peak with Blue and Violet at 100%. Cycle is from 9am to 7pm. Havent seen much Zoa growth in total, but other corals have grown noticeably even with the tank change.

Equipment: 75G Tank, 2x Nicrew HyperReef Gen 2 150W, 300W Shatterproof Heater, 2x Fluval CP2, hygger 18W CrossFlow Pump, 525GPH Canister Filter with Carbon and PhosGuard medias and foams, Protein Skimmer, ATO System.

Stocking: Snowflake Clown, Royal Gramma, Tomini Tang, Pajama Cardinal, Six Line Wrasse, Diamond Goby, Starry Blenny.

Usual Chemistry: SAL 1.025, PH ~8, AMM 0, NITRI 0, NITRA ~10-15 ppm, PHOS ~.0-.1 ppm, CALC ~380-400 ppm, KH ~7-8

CURRENT CHEMISTRY: SAL 1.025, PH 8.2, AMM 0, NITRI 0, NITRA ~7 ppm, PHOS ~.0 ppm, CALC ~380 ppm, KH 10

Bluer Photos are Before, without a lens, and Whiter Photos are current.

I am completely stumped, LFS is unsure what the issue is. Feel like I covered a lot of bases and I dont wanna keep touching anything in the tank because I know stability is what works. I really wanna save what I can. Any input is appreciated, thank you!

 

[KQuillan]

@ReefSquad

 

[Flare]

Update: Today I noticed lots of tiny air bubbles all around my tank in the water and on the rocks, and the brown algae like stuff comes back every day. Corals still slowly dying, I see a zoa polyp barely opening on some colonies, duncan is still agitated. Pink kenya tree not as shriveled as the green.
I noticed that my feather duster tubes are soft, and I saw some red worm like things with feather heads floating around the tank, assuming they are dead. Snails are still turned over and acting weird.
Fed flakes and dosed nitrogen, water parameters are the same. Turned down white light from 12% peak to 10% peak.
Attaching pictures, im assuming maybe they are Dinoflagellates?

 

[bubbgee]

Update: Today I noticed lots of tiny air bubbles all around my tank in the water and on the rocks, and the brown algae like stuff comes back every day. Corals still slowly dying, I see a zoa polyp barely opening on some colonies, duncan is still agitated. Pink kenya tree not as shriveled as the green.
I noticed that my feather duster tubes are soft, and I saw some red worm like things with feather heads floating around the tank, assuming they are dead. Snails are still turned over and acting weird.
Fed flakes and dosed nitrogen, water parameters are the same. Turned down white light from 12% peak to 10% peak.
Attaching pictures, im assuming maybe they are Dinoflagellates?

Possible cyano too.. need a microscope to positively identify. Phosphate at 0 indicates dinos though. Softies are starving for nutrients. Try to dose NeoPhos, feed reef roids to bump up phosphates to detectable range for now while you try and ID what's going on with the algae.

 

[bluemon]

How often did you do water changes before the crash? Or what was the last water change?

Water changes still should be done even if the water is “clean” (or doesn’t have nitrates)

Lowering nitrates isn’t the main purpose of water changes.

 

[Flare]

Possible cyano too.. need a microscope to positively identify. Phosphate at 0 indicates dinos though. Softies are starving for nutrients. Try to dose NeoPhos, feed reef roids to bump up phosphates to detectable range for now while you try and ID what's going on with the algae.

I will start broadcast feeding reefroids, every other day you think? Currently using NeoNitro.

Should I remove my PhosGuard media? I read silicates may contribute to Dino's, and that media removes them. However if getting Phos up is the priority then ok. My LFS will help me identify them tomorrow, and provide me a water test too, will provide another update.

My Canister filter also has a UV light which I read helps get rid of Dinos, is that right?

 

[Flare]

How often did you do water changes before the crash? Or what was the last water change?

Water changes still should be done even if the water is “clean” (or doesn’t have nitrates)

Lowering nitrates isn’t the main purpose of water changes.

I only do 5g water changes every two weeks, my purpose being to have dirtier water, LFS said that was okay to do. I never had Nitrates or Phos get near dangerous levels though, so I hadnt done any large water changes until now.

That may not have been so smart of me looking back. I have chemicals and all for reef ready to replenish the minerals that the water change would replenish but, I can see what you mean though.

Partly because im inexperienced and didnt expect less W.C. to maybe do this, and partly because I am a college student with limited funds, I buy 10G of S.W. for W.C. once every 3-4 weeks, and keep the buckets stacked in my closet.

 

[Flare]

UPDATE:
Noticed the thinning and shrinkage of corals stopped, and yesterday my zoas were all opened up and GSP. I did a final rock cleaning, sand cleaning, and water change. Pavona, Chalice, Favias, Duncans, and Cabbage coral seemed to handle it best. LFS found but couldnt name the species of Dino, but it was obviously a toxic water column pest. Replaced the UV bulb on my filter but seems the actual slot is burnt out, will have to replace, but the Dino's went away with just water changes, cleaning, and stable parameters/lighting. I have removed my PhosGuard media to get some phosphates as I assume thats why my corals werent thriving. Turbo snail and the rest are all active and eating again.