So glad its sorted Gertrude sorry about yer mother very similar situ here* but to recap ne need for bottle spring water especially since your going to be changing more frequently but you will require a very good water conditioner and several large buckets which will hold the clean conditioned water several hours before you add to tank, add correct dosage conditioner such as PRIME to buckets::: then about 30 mins before you add new water to tank bring buckets close to tank temp using boiling water and temp gauge; dirty water siphon out using the proper aquaruim siphon which has large neck especially designed to pick poo grom with the gravel use a slight twist stab

The sponge filtrate with filter cannistor never re-new this unless its falling apart lol it contains millions of beneficial bacteria that take ages to colonise but to keep them in tiptop condition every 3/4 weeks remove and rinse out in some of the old water removed from tank but never tap water, if you have actual carbon subtrate(not sponge)this can be replaced regular

Am sure your already aware of most above but a good recap might help new readers