hi there,
meaning ur tank will be 1ft width?
30 x 45 x 30cm?
if really 1ft tank, i will go for length rather than height.

1) how frequent?
what u mean by setup? all those equipment or scape?
ADA soil yes, from ADA Japan they also mentioned can use 2~3 years...
but go check the huge tank from Mr. Amano, more than 2~3years already
2~3 years, consider long duration already
2) what sand? sirui sand?
If sirui sand, do you read the instruction at the plastic there? wash before use...
now only u can do is, WC more frequent...

LOL~!... that's what u meant huh... hehehe.. no la, actually that's a myth. 9 years no need to fertilize anything, mosses or anubias or perhaps some ferns might do it... but all these 3 dont need the base fert anyway.

but yes, it does helps you when like ...erm... you forgot to fertilize on that day, or perhaps you were out station, or you dun want to be binded with the dicipline to squirt the fert every morning...

take it like this, when the plant cant find the traces in the water column, at least they got another alternate source of "food" in your tank already. some plant (like the 3 above i mentioned earlier) dont have roots in the soil. but unlike those 3 above, some plants do still need fert... so their only source of food is in the water column which will be come from your liquid fert.

but on the other hand, those plant that have roots inside the soil, they will still looking for fert in the base with their roots. haiz....now so pusin pusing already...bleh~!

to make it simple, those 5 trace elements as your base fert is in the soil. the liquid fert is in your water column. if you;re a plant, you'll be more happier rite when u can get food from anywhere in the environment around you. from bottom, from above...when you;re happy, you sure will be good ma...in the plant case, they'll thrive better

psht.... im starting to BSing already.... ignore any part that arent contains any info...

yes...some ppl do put some soda bicarbonate

to make co2 release faster gua...
i also DIY co2...didnt setup anything to pressurize the co2...co2 also will flow thru the diffuser...