Thats a common assumption made from those who kept larger tanks, or smaller tanks that suffer from topoff and testing hassles. These vase reefs do not require water testing, ever, except for what you need at water change time, a temp indicator and a swingarm hydrometer. Refractometers are highly optional and never required in reefkeeping, so the testing question has been addressed, there isn't any.
These reefs are less work than any other reeftank or I wouldn't own one...my other hobbies are much more costly lol and its the stability of this tank compared to other setups that make it outlast the other setups we often compare to...
When you change out all, and not part of the water, you reset the ion and chemical palette to neutral, nsw levels, thats why you don't test for anything. We don't use fish, so there is nothing to die and leak ammonia, therefore we just opted out of nitrate, phosphate, silicate, ammonia, calcium and alk testing
try doing that with any other reef
the topoff is once a week now with the setup muskieboy is describing, a trick invented by cichlidmania26 off youtube that can make a reefbowl go up to 14 days in between a single topoff (he did this while on business trips)
but thats extreme muskie..so the normal way to condition your tank when you are at home and not trying to stetch out the care (dont skip the weekly water changes etc) is to never allow your salinity to creep outside of 1.023 to 1.024
however much evaporation time you get in between that interval is how long you get in between topoffs.
The most common method is to change your water and set the sg at .023, use a felt tip marker to dot the water line on the outside of the vase neck. A half inch drop is this range mentioned above, when using the same vase we have
the blended powerhead/airstone method is solid. When you set up the vase just use sand and rock from an established tank and corals can go in on day one, Ive done it all the time like that. Don't use the old water, make up new water each water change for these gallon picos, if you don't, expect algae invasions soon.
If you use old live sand from a reeftank, you have to rinse the organics out of it totally or you can expect an algae crash. The filtration bacteria from the sand are not needed, the LR alone will do it, so the sand is incidental and only for looks. Personally Id never use diaper sand from another reef tank, I always use arrive alive wet pack fiji pink from natures ocean, zero organic loading to concern about. Its mainly the cycled LR that allows you to set up corals on day one.
Have the vase up and running with water and known topoff intervals before putting in corals. You need to make sure your lid interface works (the hardest part to get right_) and then if that works its all good to go. If this is a rather short term endeavor until you upgrade, just do the weekly feeding and full water changes and that will work. if this is intended to be a long term, stand alone reef tank then you have to dose with two part on top of the water changes, wc alone will not do it long term regardless of what anyone says about a gallon reef.
Some people want a tank that holds fish, so start with a 10 gallon on up if thats the case...but if you want to keep inverts and any species of coral that fits in the bowl cheaper and more stable than any other sized nano reef, with less topoff, zero water testing and total predicability then thats what these bowls are for. This vase is more stable and easier to run with less work than any other tank, but there are obvious stocking restrictions so you have to consider that before pico reefing. It is easier to run that 5, 10 ,15 gallon nano reefs etc in terms of weekly work and dollars spent in constant adjustment of params which is not needed here.
The reason this reef is the longest lived pico reef in the world is because it requires no testing and is more stable than any other pico reef design, so far.