Hi Folks,

After I installed my algae scrubber my PH went from 6.8 to 7.6. Maybe 8 sometimes. Been running this thing during the day for a year and then shut it off at night. However, over the last 6 months I've been running it all night long (with light off during the night). I had 4 cory cats (peppered, melini, albino, and emerald). Also one rubber lipped pleco. I've had these guys since 2015 approx. Pepper died last week from what looked to be a swollen gill flap. Tried antibiotics (Kanaplex) and it didn't help. Then I was thinking maybe it was gill flukes so I got some anti parasitical (API general cure) that I'm going to try on the rest of the fish. So this morning I wake up and I see my rubber lipped pleco lying on his back at the bottom of my tank. Oh sh . . . I flipped him over and he's alive. However, that doesn't mean he's good. He looks really dark. He usually hides during the daytime unless there is a water change so this is bad news.

My tank has been cycled for a few years and I changed about 50% of the water every 10 days. I checked the parameters today. PH - 7.5, Ammonia - 0, nitrites - 0, nitrates - 5 ppm. 20 gallon tank. Water temp varies between 75-80 (depends on what thermometer I use to check it).

My question is whether the raised PH could be harm the fish?

Rubber lipped pleco ph - 6-8
http://www.aquariumlife.net/profiles...eco/100074.asp
or
6.5 - 7.5
http://www.liveaquaria.com/product/1...c=830+837+1004

Emerald cory cat
ph 5-8
https://en.wikipedia.org/wiki/Emerald_catfish
Melini cory cat
ph 6-8
https://en.wikipedia.org/wiki/Corydoras_melini
albino cory cat
ph 6-8
http://animal-world.com/encyclo/fresh/catfish/acory.php

Any advice would be appreciated.