DWC reservoir size for recirculating system?

-6 buckets at 5 gallon each
-1 bucket for a control bucket

Water will auto top off and my water comes in at about 7 ph and 30ppm.

Do i need to add another larger reservoir to the system? Or should I leave it as is with just the 5 gal extra reservoir. I check PH daily. Is there any benefit to a larger res besides PH and nute stability? I'm thinking with less water total that changeouts will need to be done much less often.

Smaller containers = less water = less work.

i wouldn't have water flowing into the system at a ph of 7 - that could bite you in the ass real quick. i'm looking into doing a similar setup for my second grow, multiplanted tubs are a pita for anyone determined to wash their shit out regularly.

my plan is to have 8 individually plumbed 5g buckets so i can move them if/when i need to and two small (maybe 10g) tubs stacked as the reservior. the lower tub will control the solution level in the buckets by use of a float valve fed from the upper tub containing only 5.8 ph'ed water. my 5g buckets will only have about 3g each (4 for the first couple weeks) and that's 15-20g, another 8 in the 10g tub makes 23-28g of solution at a time, depending on plant's root development. a 25 gallon nutrient regimen would serve such a setup well and if space permitted i could even throw more buckets on, it'd be expandable/collapsible. throughout the week there's only be daily water quality checks and topping off the 10g of ph'ed water as needed.

I'm going to have a reservoir of about 5gal for the fresh incoming water to go into, then it will distribute water to the veg and flower setups. I can ph that water if it becomes needed. My tap water is 30 ppm and about 7ph, after adding nutes it ends up at 6.5-7.0 so hopefully ph will stay fairly stable and easy to adjust down.