Emergency! My Fish Are Dying!

[ihavefish!]

I will apologize in advance that I have not read the stickies but we have an emergency and it's 11:47p at night so I will have to send hubby to Wal-Mart if you suggest it.

Stats-
75 gallon freshwater
Occupants- (2) large breeding angelfish, and approximately 30 other small tetras/gourami's,1 shark, 1 molly, 3 zebrafish- all are friendly community fish.
Tank has been up and running 5 + years- never any problems.
Chlorine-0
Nitrate-O
Ammonia-0

Everything else was good except my PH is sky high- 8.6ish. I am now losing 1-2 fish per day- began this past weekend- so we are down about 8- all three pink gourami's have died, 1 shark, and a few miscellaneous tetras. Some of my little ones are looking really raggedy. All seem to be sick except for some of the bigger tetras and the angels but I am afraid they will be start next. No signs of fungus or anything else like that from what I can see.

Have been using Cycle for years, 1x/week- no issues and all seemed well. We change 25% of the water every 4 weeks and the filter is cleaned every 4 weeks on opposite 2 week schedule.

No new fish have been introduced to tank in 6+ months.

Last water change was 10 days ago- cleaned filter again this past Saturday.

No change in temperature and light is on 10 hrs per day, 11a-9pm.

Any advice would be appreciated!

 

[WILDER]

What test kit are you using.
What your tap ph reading.
Do you have a nitrite reading.
What substrate and ornaments do you have in the tank.
You should be doing a water change and gravel vac once a week.
When you clean the filter do you rinse the sponges in old tank water or tap water.

You shouldn't need to use cycle once the tank has cycled. Not even proven it works.
Is it nutrafin cycle product.

Are the fish showing any of these signs.
Darting, erratic swimming, excess mucas, being listless and not noticing there surroundings, turning upside down, unable to maintain balance, gasping.

 

[ihavefish!]

I'm at work right now so I couldn't tell you the other info but my hubby took the deceased fish and a couple of the really bad small ones to the pet store- all the water readings are good- this appears to be fin rot. They told us to use Melafix so we bought that and are going to do our best to save the ones we can. What a mess!

 

[WILDER]

Melafix is only good when the fins are beginning to heal.
You need an internal bacteria med. melafix is an external med.