@SunnyX First, great write up! I've been carbon dosing now for about a year on my 340 gallon mixed reef. I run many types of filtration as my carbon dosing levels are very high to maintain my target nutrients. First off, and most important, the problems I'm solving for:
1. High nitrates in a mixed reef - I hit nitrates of 40 ppm while dosing 55 ml a day of vodka.
2. High phosphates - hit .40 ppm while carbon dosing 55 ml per day.
3. Coral growth stunted
4. Corals dieing off - I've lost close to $1000 worth of hammers, elegance, mostly LPS corals. Even my toad stool started losing flesh.
5. No water changes
With that said, the filtration I'm running to just to maintain cleanliness:
1. Oversized skimmer - rated for 500 gallons moderate load.
2. Well established Algae turf scrubber
3. I ran matrix rock in a cannister filter, have since put the 25 micron cartridge back due to vodka dosing (will identify reasons later).
4. Just installed a red Sea 1200 Roller mat - Going through rolls of paper within 10-12 days right now. (I believe this to be due to vodka dosing based on #3)
So, that said, My response to the issues was to gradually increase my vodka dosing. I've gone from being at 55ml per for the past year to 75 ml per day over the last 3 months. Since then, My nitrates have gone from 40 down to 27. And my phosphates have been reduced to .08 (in combination with dosing very lightly phosphate-e - around 6 ml once to twice per week depending on if levels are increasing or remaining the same.)
So, it's working to get things down to where I would like. I would like nitrates to remain steady at 15 - 25, and phosphates to remain between .05 and .1. I have a couple SPS that do not like the lowered nutrient values at all. They've endured some bleaching, but many polyps are still open and appear to be coming back as they adapt to the new nutrient levels. Other SPS are flourishing now that things are more in check..
So, if things are going in the right direction, why this write up? Well, simply put, bacterial slime! I think the slime itself was possibly damaging some of my corals. I have slime covering my overflow teeth, my gyres were covered in slime (I'm not sure how they even were running, so much slime on the blades) within 2-3 weeks they have slime all over them). My skimmer is constantly pulling out black water. The paper on my roller mat is covered in a thick jellylike slime, and my 25 micron cannister filter was covered in slime as well. I'm having to wash basically everything in the tank within 2-3 weeks due to the amount of bacterial slime.
My PH probe is showing PH just getting to 8.05 and 7.97 at night. It used to easily get to 8.2 - 8.4 during the day and 8.1 at night. Going from 55 ml a day to 75 ml per day has had huge impacts.
My return pump intake screen is covered in slime within 3-4 days reducing my flow to the tank. I have a reeflo hammerhead external return pump. I'm scared to take it a part to see how much slime is inside it.
I don't know how healthy it is for that much thick slime to be in the water column for fish to be swimming in. Maybe adding in the reef mat and 25 micron cannister cartridge will solve the problem, but I can't afford to replace a $30 roller of roller paper 3-4 times a month. . .
So, how do you deal with bacterial slime? I like where my nutrients are going, but, I don't like the slime monster!
I only see what you put here 
