I am working on a FOWLR
tank for a friend, 135g w/15 sump so 150g system volume. The pH is 7.4 and KH
is about 4 dKH
, salinity 32 SG
1.0235 and it's SUPER dirty. No protein skimmer (he's got one on the way) and it's been running for about 3 years. Cyano
all over the place. I am going to do a 40 gallon PWC
w/IO sea salt and RO
water and clean all the Cyano
and detrius out. Inhabitants are 1 dog-faced puffer, 1 Yellow Tang, 3 Sergeant Majors. He only has about 40-60 lb of LR
. So lots of issue to tackle on this tank.
My question is this: the new water generally runs at a pH of about 8.2-8.4 and KH
of about 7 or 8 after the salt is mixed in.
The way I calculate it, if he has 150g and I remove 40, that leaves 110g of 7.4 pH 4 dKH
water. If I add 40 gallons of 8.4 pH 8 KH
water, and go by a linear mixing calculation, then his pH will raise to 7.6 and KH
will raise to just over 5. Is this an acceptable pH swing, or should I raise the pH/KH
in his system prior to doing the water change?
I understand and pH is not a linear scale, but KH
is. So my calculation may be off and I don't want to throw the pH too much too fast, for obvious reasons.
I was planning on dosing his tank with Brightwell Aquatics Alkalin8.3-P today before doing the PWC
& cleaning tomorrow. The jar says exactly how much it will change the KH
per unit dosed, but says nothing about how it will affect the pH, so I figure the less the better just in case.
The instructions say that you make a stock solution, and 1mL of this solution will increase dKH
of 1 gallon by 0.36. It also says if the initial dKH
is below 7, to add the maximum dose of 10ml per 20 USG (or 1/2 mL per gallon) until desired alkalinity is reached. This means that it would only raise the dKH
of the entire system by 0.18 per dose. Is this considered to be the safest rate of increase of KH
Anyone have any insights??
I just went through a calculation taking into consideration the logarithmic nature of pH and figured that the water change will raise the pH to about 7.9, or half a point. Is that acceptable? Or should I just do a 20 gallon change to be safe? That would raise it to 7.7-7.8.