Soapy film on water

Question
QUESTION: I have a 75Gallon tank, salinity, nitrates, pH, ammonia etc ALL at ideal levels.  I have an assortment of fish. I have a rena filter and a remora pro protein skimmer.  About 4 weeks ago I added some red algae additive to the tank.  It removed most but not all of the red algae, I then did the recommended water swap.  I put the skimmer on and it is overflowing into a 5 gallon bucket filling the bucket as fast as it can.  I have now done in 4 weeks, 5 water swaps of 20 gallons... AND ran the skimmer and poured out another 5 jugs that it skimmed.  I have my skimmer off now because I am afraid it will overflow when I'm out and even with all the parameters fine 2 tangs died the other day (no diseases apparent) and I STILL have a bubbly film on the top of the water... I don't know what to do.  I use all RO water from a reputable place and use instant ocean salt.  Any help would be appreciated.  Thank you.

ANSWER: Hey Mike,
A film on the surface of your aquarium could be from numerous causes, water break/surface disruption from powerheads or the inlet, protein, excessive food and detritus decaying, any additives(water conditioners, supplements, etc) you may use. The film could be caused by the algae remover(I assume thats the purpose of the additive). While most algae removers claim to be harmless to your fish, most contain additives that can cause problems with your inhabitants and biological filter(bacterial colonies) if not used in EXACT dosage. What most people have that they consider red algae is cyanobacteria. A sign of a nutrient rich environment. While cyanobacteria can be an effective nutrient filter and cause no water quality issues, they can also be toxic to fish if eaten and overtake healthy alga in the system. It is best to remove it manually and get rid of it through hand removal, lowering lighting periods and reducing foods(the amount fed, not the frequency). If your water quality is in the green and all levels are good I would think the foam is derived from the treatment.
The skimmer should not be working this hard. I would check the settings of your skimmer and also check for mechanical malfunction. Micro bubbles from a faulty or bad setting on a skimmer can also cause the bubbly, foamy look.
As far as the dead tangs, it could have been the algae treatment or the stress of the numerous water changes(and unfortunately the truth is sometimes fish just die and we have no reason). Were they eating and acting their norma selves before they died? Or were they hiding alot of the time and not taking foods? The latter are signs of stress from environment or ailment.
After the treatment and the recommended water change for the treatment, if your water parameters are fine, you should do no more than 1 water change(20 to 25%) every 3 or 4 weeks. Cleaning the filters and media a few days before the change so as not to disrupt the biological filter too much and remove as much detritus as possible. I would also take a look at the water level in the system, how much surface break/disruption you are getting, and also the amount of water conditioner added each water change. Both of these could be the cause if your water tests show good levels. I wish I could be more specific, but from the information at hand you have a number of possibilities to look at. Let me know if I can help further.

---------- FOLLOW-UP ----------

QUESTION: Thanks for the help I'm thinking the stress may have caused the losses.  I figured the additive (which I won't use again) caused the water to be soapy but I figured with the amount of water changed that it would be out of the system.  Regarding surface break/disruption, I have 2 power heads but both point fairly straight (not towards the surface) and my filter which I normally keep under the surface, what should I have?  Do I need something breaking the surface, maybe even an airstone?
Oh... my protein skimmer has no adjustable settings.
Thanks again I really appreciate the help.

Answer
Hey Mike,
Glad to help. The additive can take a week or two to be completely gone even with massive water changes. It's everywhere, rock, substrate, filter media... etc., and you definitely dont want to do a cleaning that deep. There would be devastating effects on the biological filter. Adding carbon will help remove it. No need to move the powerheads or the filtration. You want some surface disruption and break, but too much can cause/increase the foamy appearance as well. Thats the only reason I asked. In regard to the protein skimmer, read the instructions again, or look them up on line, look for specs regarding flow rate, water column and aeration inside the water column. I personally dont use protein skimmers, but a good unit will have some adjustment for the bubbles/aeration in the water column. The way it works is the protein is brought into the column, attaches to the bubbles and is removed. It may just be a faulty unit or have a malfunction.  Let me know how it goes.