Our tap ph is very high about 7.8 and I usually add PH down drops to the weekly water changes. For my new tank set up, so far there are no fish in it only plants, I would appreciate advice re lowering it. ie Just add ph drops to lower it and if so would it be okay to work out how many drops are needed and do it all at ones, or do it gradually. Or does anybody else have any suggestions for me. Thanks.

If the fish are used to that pH I would leave it alone. Better to be wrong but stable than fluctuating as you try and lower it. The pH Down is not good to use in my opinion as it is only temporary due to buffering effects in the water.

Driftwood will lower pH as will peat in the filter (put it in a fine mesh bag or old pantyhose) and lots of plants.

agreed, those ph up and down products are often only temporary. the kh of your water will most likely be contributing to the high ph and those lowering products wont fix the kh which means it will soon rise back up. most fish are able to adapt to that ph but species like apistos etc will prefer lower

if you really need to lower it using peat as caryl suggested will lower both ph and kh but it may give you a slight tea coloured tint to the water (some people dont like it). it will need replacing every now and again but im not sure how often, perhaps monthly? the problem that comes with altering your water is you may have to alter the water your putting in each w/c if there is quite a difference from your tank and your tap

Yeah I'd leave it alone. Its easy to increase KH/pH, but its too much effort to lower it unless you absolutely have to.

Also agree pH up and down are temporary and a waste of money. You'd either need to use peat or reverse osmosis to lower the kH effictively.

Best to just get the fish used to your tap water, 7.8 is fine, also test your tap water 24 hours after you've taken it from the tap, often you'll find the pH changes as various gases evaporate.