figured out the reason for ph spike

Question
Hi Christy,
here Madhav again, this time not an issue but a good news
u remember a long time back i asked you the question about ph level in my tank, it was 8.4,
just to update you, now finally i figured out the reason why ph in my tank was so high, the reason is substrate,
i dont know what is there in that substrate but the LFS owner shown me the same substrate in his tank, but neon tetras are doing fine in that tank.
(i dont know, he might be changing them frequently). fortunately i want to give it a try with the new substrate "contr soil" from japan made by www.marfeid.com",
so for the past three months, i was removing the existing substrate every weekend. 3 weeks back i added this new substrate, to be on safe side
i returned all the fish to my neighbour LFS ( i compromised with mollies and swordtails and guppies with a ph of 8.2) during this period anubias nana and water wisteria survived in my tank.
once i added this new substrate (added slowly with a tumbler, water at lower level was a bit cloudy for an hour or so after that water is very clear) i added 10 H. rasboras, now the ph is 6.6 and after that i added 5 rummy nose each week for 2 weeks, so now there r 10 rummy nose and 10 h rasbora in my tank
all are happy no fish deaths, ammonia and nitrite and nitrates all are zero.
and i am happy that i can grow some plants, where i earlier failed.

so if any one posted any question on substrate selection or high level of ph, pls ask them to use known and proven substrates(i regret, i didn't even consider the substrate at all when i setup the tank, i blindly followed the LFS guy instructions)
i didn't want to buy so expensive "eco complete" or "flourite" that time and i have chosen cheap S$20.00/10kg but after that i spend more than S$100 for either fish or plants.
i know everyday  u receive many emails from novice hobbyists like me, only thing i can suggest from my experience is consider substrate as an important element in whole system and choose right kind that suit to their fish and plants, that they intend to have.

thank u very much for guiding me all the way
bye for now
Madhav

Answer
Hi Madhav
Thanks for the update!  That does make sense though.  But didn't you try testing the substrate in a separate bowl?
Well, at least you figured it out and it finally worked out.  Hopefully the plants will grow now :)  I'm sure they'll love the lower ph and will thrive now!  
Sometimes it doesn't pay to take the cheaper way, I've learned that lesson with other things lol.  You get what you pay for.....Good luck!

Christy