Whats the GPH on the stock filter pump?
-If there is anyway to swap out the pump with one that has a bit more flow this could help by improving water flow in the tank. This does a couple of things. It increases oxygen and it keeps derbis in suspension longer and allows your filter to preform a lot better .
What kind of snails do you have?
- Some snails such as Nassarious and Cerith snails do a lot better job sifting and stirring the sand and eating the crude that builds up in it often times. Turbos, Astreas, and Trochus are better suited to cleaning the rocks and glass.
Thats interesting that you mention the light bulb change with the out break of slime algae. While it obviously was a factor I think that its more of a case of "the straw that broke the camels back". You should be using 10,000K Marine grade lamps for your light fixture. If your using 6,500K bulbs this could have a marked effect on your tank as this kelvin rating of bulb is better at growing algae than the 10,000K's are. This might explain why after a bulb change this suddenly reared its ugly head.
Basically red slime is more related to bacteria as opposed to actual algae. It usually occurs in nutrient rich tanks, with heavy fish loads, with filtration thats lacking, water flow thats lacking allowing for dead spots in the tank which is where this problem will usually first show itself. If you remove the cyno and it immediately crops up in the same exact spot then this is a good sign that you need better flow in the tank in that area.
I dont think all of these exist in your tank but its possible a few of them do. Look at your tank hard objectively and see if there is anything you can do to elimenate any of the above percursers that over the last 2 years has finally added up to this problem with the bulbs being changed. I have found that when faced with a problem like this its better to change one thing at a time and allow for some time to pass instead of changing many things simulatniously. It will better allow for you to nail down what exactly the root source is so you can better deal with it.
Your doing a lot of things right for sure which makes this a tough one to nail down.
1. Since the light was the "difference" check the bulbs to make sure they are 10,000K's.
2. Next move I would make is to remove manually as much as you possibly can. Getting as much of this stuff out of the tank will be a nutrient removal technique. The nutrients this bacteria has absorbed and locked up will be released back into the system if it dies back.
3. I would do is quit feeding the corals if they are photo-synthetic, maybe feed a minimal amount once a month instead of weekly. The purpose behind this is to cut back on adding any unneccessary nutrients to the tank.
4. I would also try and boost the flow in the tank a bit. I realize the target is 10 X minimum. If you got this and you think your corals can handle it add a little more. Something like a Korallia Nano might be the ticket. If this is not an option prehaps a bigger filter pump with a few GPH more than the stock.
5. I doubt there is a skimmer thats small enough to fit yet still be effective but this is truely an amazing piece of gear. If ones not available for your tank, then frequent small water changes more so than what your currently doing might be in order. I do weekly 20% water changes in my tanks. Recently I have also went back to using skimmers as well. I am absolutely stunned at the amount of gunk comming from the skimmer cup!!! One would have thought with the amount of water changes I do that this would not be the case.
6. Im not sure if there are any resins that yiu could run in your filter that would really be all that effective, maybe someone can chime in thats a bit more knowledgable in this area.
If your in danger of being over ran with this to the point your corals may suffer...you can use Chemi-clean. Its an oxidizer that is very effective at elimenating it...temporarly though. Its treating the symtoms not the cause so it does little more for you than be a bandaid on a cut throat. It will however buy you some time. After dosing the tank with this as per the directions do a large water change and use a lot of carbon in the filter to soak up the nutrients that will be released as the cyno dies off in the tank.
Im all out of ideas beyond this...hope this helps out a bit or at least gives you some ideas from which to work.
