Today is the big day! I received my sodium percarbonate last night, in good condition. So, I decided to start testing today. The parameters for my tank are:
45 gallon tank (nominal size)(about 35 gallons of water)
SMS substrate with underlayer of river silt
110 watts of GE9325K PC light raised 6 inches above tank, on 8 hours per day
Water temperature 75F to 85F, depending on room temperature.
Water changed continuously, with dripping flow of inlet water, about 5 gallons per day.
Anubias nana petite
Microsorum pteropus narrow leaf
Cryptocoryne wendtii, various varieties
2 - Yoyo Loaches
8 - "Lambchop" Rasboras
4 - Otocinclus
About 15 Guppies
About 4-5 Endlers Live Bearer
Structure of African bog wood roots
Small pieces of same wood, with plants tied to them
Filter outlet pipe
Filter inlet pipe
Present condition of tank: Small BBA areas on some leafs, mostly anubias and Java ferns. Small amount on hardscape. Small areas of GSA on anubias and Crypt leaves. Small tufts of BBA on protruding old roots in substrate.
Fertilizing: By EI method, adjusted for daily dosing, with all fertilizers dosed at one time using two solutions, one of CSM+B+extra iron plus epsom salts, one of KNO3 and KH2PO4. Excel dosed at 10 ml per day, squirted on BBA areas under water. CO2 at bubble rate to keep drop checker in yellow-green area all day, off at night.
Sodium Percarbonate recommended dosage - 1.5 Tablespoon per 100 gallons
For 35 gallons, recommended dosage is about 1.5 Teaspoon
First dosage, .5 teaspoon, will be sprinkled over wood structure, with filter and Koralia pump turned off, about one hour after fertilizing and feeding fish.
But, first I have been looking into what possible bad effects I might run into. Sodium percarbonate is a compound of sodium carbonate and hydrogen peroxide, which releases hydrogen peroxide when in water. The possible effects would be from the peroxide, from the sodium or from the carbonate. Sodium percarbonate is about 29% sodium, compared to sodium bicarbonate, which is about 27% sodium, so the effect of the sodium should be about the same as for dosing baking soda to raise the KH. Sodium percarbonate is about 38% carbonate, compared to sodium bicarbonate which is about 71% carbonate, so the increase in KH due to sodium percarbonate should be about half of that for baking soda. Neither of these is at all likely to be a problem, when dosed with amounts comparable to that used for baking soda to raise KH. Hydrogen peroxide can be a problem for plants, fish and algae, but it lasts only for a short time in the aquarium water, so it isn't likely that it will be harmful to the plants or fish, given that some people dose 3% hydrogen peroxide in their tanks routinely when trying to kill algae. But, this is the big unknown, where the effect of the sodium and carbonate are not unknown.
.5 teaspoon of sodium percarbonate will only raise my KH about .4 dKH.
I will measure my tank water KH, GH and pH before and after the test. I will decide whether to do a major water change after the test based on what I see in the tank.