maybe a little higher. i got seachem malawi/ victoria buffer from the LFS it says to use during water changes to maintain, once youve met the ph desired. it also says to use one teaspoon for each 10 to 20 gallon. so when im doing the water change i shouldnt use a full teaspoon if i need to raise it?
You need to do the math on your wcs. Say you have a 100g tank and you are at your desired ph. You do a 50% wc with the same water as before (meaning ph levels) you want to dose for 50 gallons or half the whole amount you used on the full dose for 100g. This way everything stays the same.
I have a 55 gallon, normally taking about 15 gallons out on the water change per week so id add a little under a teaspoon maybe a half teaspoon per say. would that be to much of a spike at once and agitate the fish or should i fluctuate that amount over lets say two or three water changes
Anything between 7 and 8.5 should be fine if it's between those two out of the tap.
Test and post your KH results, and test tank water pH after a water change and prior to your regular scheduled water change. If there isn't a drastic difference in pH between the two then you're better off leaving things as they are and not messing about with altering the pH.
A stable low pH is much better than one that swings from mid 7's to 8's with water changes.
What i do when figuring out formulas is drain the desired amount into 5g buckets and mark the tank somewhere. You might need a tub of some sort to put 15g in but I would add the 15 gallons to a tub and add your solution. Circulate the water with an airstone or power head and test 24 hours later then 48 hrs later . Check your readings and adjust accordingly. You are doing roughly a 30% wc so base your dose as 30% of the full 100.