Fish "randomly" Dying

[Gruffle]

hi, over the last couple of weeks a fair few of my fish have died, and i have no idea why, heres my setup

160L tank, set to 26 degrees c, 2 filters, one internal, one external, tank has been running for a couple of years with no problem

current inmates were 1x BN plec, 2x krib, 2x keyhole cichlid, 1x RTBS, 6x serpae tetra

in the last few months we've lost 2 tetra, one keyhole cichlid, one krib and the RTBS last night

checked the water chemistry last night, results below:

ammonia - 0
nitrates - 5ppm
nitrites - 0
ph - 8.2

my tapwater ph is 6.8, but when i add water conditioner it goes up to 8.0 ish

this was my initial most likely culprit but i dunno..presumably the ph will have been creeping up and up but i'm not sure what i can do about, i can chemically alter the ph but sending it crashing down to 6.8 will probably do as much harm as good, and changing the water will do no good if my water conditioner is sending the ph up to around 8.0

i have an open topped tank so it's not outside the realms of possibility one of my kids have dropped something in the tank, although i can't see anything...

 

[fishprotector]

Which water conditioner do you use?

 

[Gruffle]

Which water conditioner do you use?

i used the tetra one in the yellow bottle, although in the past i've used the nutrafin one, so bought a bottle of that today, same results, tapwater ph going up to 7.8 in the bucket...

 

[WILDER]

What your tap PH
Brand Name of test kit.

Are the fish showing any symptoms.

 

[Gruffle]

tap ph is 6.8, although when i add water conditioner it goes up to 8.2 with tetra safe+ or whatever it's called and 7.8 with nutrafin aqua+ (although i only realised this yesterday, so god knows how long it's been happening...)

test kit is a nutrafin master kit.

remaining fish appear fine, the keyhole is very mottled, but that goes on and off, even the RTBS was fine in appearance until a couple of hours before it died (although it was 5 years old...so i dunno...old age mebbe?), deep black with dark red fins, it was very evident when it was upset

 

[WILDER]

Are your fish showing any signs of ph shock..


H Shock
As its name suggests this condition occurs when a fish is introduced to quickly into a new environment which has a very different pH from the one it came from, when the pH is adjusted to quickly and the fish have little or no time to adjust themselves, or when the pH is to far outside the fishes normal range.
It is very important that any change in water chemistry is made slowly and fish should never be exposed to changes of pH greater than 0.5 of one unit on the pH scale in either direction.
Avoidance is by far the best solution because in most cases the symptoms don't appear until the second or third day by which time the damage has been done and the fish will probably die.

A fish suffering from this condition will show all the typical signs of shock.
Lying on the bottom and paying little or no attention to its surroundings and ignoring potential threats.
It may even lay on its side or go upside down completely. <br />There could be other signs to, related to Acidosis and Alkalosis.
Excessive mucus production.
Rapid breathing.
Swollen abdomen. (Alkalosis only).
If the condition is allowed to go on for one or two days then the chances of a successful remedy are greatly reduced because a lot of damage will have taken place. If the symptoms are spotted early enough there are a couple of things that will help.<br /><br />Begin to return the pH to the original pH in steps of 0.4 of one unit on the pH scale and allow 3 hrs in between the adjustments. Make these adjustments until the pH is returned to a safe and satisfactory level.

Treat the tank with a broad spectrum anti-Bacteria/Fungus compound to prevent secondary infections of the Skin and Gills.
Prevention is easy. A successful treatment isn't
PH SHOCK LINK<br />http/groups.msn.com/FishHealth/phshock.msnw<br />http: