combining fish & bacterial infection?

Question
I just lost my 10 year old 14-16" comet goldfish.  My daughter got it at the carnival.  Went belly up yesterday, tried peas but he went really quick.  I bought him a friend 1-2 years ago and put them both in a 120 gal tank.  2nd comet is now 12 inches and has white but not fuzzy around his mouth.  I treated him for cotton mouth about 1 year ago.  It has not gotten any worse or better.  Should it go away or do you think is mouth is damaged?  I could send you a photo if it would help.  I'm asking because I have 2 other 30 gal tanks that I would like to combine all the fish into 1, less maintenance.  I have adjusted all the tanks to the highest or lowest temp and pH levels that the fish will tolerate hoping everyone will get along.  The comet goldfish in the 120 gal tank is 75 deg F with a pH of 7.5 (should be around 70 & 8.0).  I have 2 clown loaches and about 8 small tetras in another tank at 76 deg F with a pH of 7.6 (should be around 78 & 7.0).  Each have been this way for about 6 months.  The 3rd 30 gal tank has a mean old 12-14" pleco in it.  He does not play well with larger fish so I'm going to keep him alone.  Do you think all will survive?  I'd have to lower the salt with changes for the smaller fish, the goldfish can only tolerate a smaller dose.
1.  Should I treat comet goldfish mouth before combining fish?
2. Will they be OK together?
3. I have a dark green feathery algae on the back wall only and I don't know how to get rid of it the 120 gal tank, except to scrap it.  Will the floating algae hurt the goldfish?

Answer
Hi Judy,
I'm sorry to hear your lost your comet goldfish. Its amazing how long goldies can live. Ten years is quite a wonder!

I think you should probably be alright with combining those fish you mentioned. But like with anything, sometimes you have to try it out and see how everyone gets along. They should be fine. But be sure to watch them closely. You shouldn't have to add salt to your aquarium. Although its often recommended, salt does not do fish much good except when they are truly sick. It can be a good side-treatment to a medication.

I'm not too sure about the white around the mouth of the second comet. I'd say its probably just natural coloring but if you're worried you can send me a picture through this email address -    nature_girl2u@hotmail.com

The dark green feathery algae is probably due to excess light and/or nutrient levels. It won't hurt the goldfish if it floats around -- in fact they will probably eat it. ;-)

Try not to adjust your pH too much. Its much easier to just let your fish adapt to your tap water's pH than to constantly doctor it. pH fluctuations are very stressful for fish.

I really hope this helps!
Happy holidays,
Karen~