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Discussion Starter · #1 ·
Black basalt sand is cheap in Hawaii but in a jar of 50/50 sand to RO water (7.0 initial pH) it raises the ph to 8.5. I am doing a high-tech tank with mineralized soil (my initial soil pH is 7.5). I would like to have pH in the range of 6.5-7.5 and am concerned about the sand. Thoughts? Not sure why it raises the ph so much but was thinking that perhaps included minerals might be affecting it. How about an acid wash with lots of rinsing to try to react those minerals? Or underlying a peat layer?
 

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Discussion Starter · #3 ·
Ok, so I found that a relatively small amount of muriatic acid seemed to neutralize the sand (add more acid and no further bubbles). So I added enough water to barely cover the sand and about a quart of hcl. It's been bubbling and I've been stirring. My thought is that a small amount of coral sand or powder contaminates the basalt sand. Depending on how much I hopefully can dissolve it out. I'll report back with new ph when I finish. I think that this would be relevant to anyone using Hawaiian black sand.
 

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Discussion Starter · #4 ·
Hey Sketch, keep me posted - still might use some peat. Somewhere I read a mineralized soil recipe that advised a layer of peat between the soil and sand but can't find where I saw it. What happens to peat longterm, and do you start to lose the hardness reduction effect over time?
 

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im still new to this hobby, so this is from everything i recall reading on the internet, might be right, might be wrong:

peat decomposes to produce nitrate i think, which is needed by the plants. however peat does not contain much nutrient, therefore nutrients are provided via a more fertile layer of soil, or ferts. i believe the peat will lose its ability to reduce pH over time. George Farmer grew hairgrass using inert sand in his iwagumi scape, nutrients are provided via ferts. this is what inspired me to try growing using sand.

well, im leaving for a holiday trip tomoro, i'll collect some sand from the beach and test how long the peat lasts. =) if this works, i wont ever spend money buying sand again. the beach will provide all the sand i need.
 

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Discussion Starter · #6 ·
hey Sketch,

if you are using beach sand that is from coral, it isnt going to work...it is made of calcium carbonate, which is alkaline and a buffer. Unless the sand is silica or quartz beach sand. Need to find some more inert sand.

after about a dozen rinses, ph of the basalt sand is 6.0 will rinse some more and retest later
 
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