Hey Robyn,

This one's gonna be a really frustrating one for me to ask cause I cannot think of how its possible that I cannot find either an algorythm, survey, or any online documentation as to how much ice to expect on my pond according to my dimensions - and worsed:

the aquascape designer down the block claims he's never received more then say 5", my friend an aquascape builder and landscaper claims the most, he'd guess, to expect is 12"; the later fits into your 10" you received one year, but your winters are not as cold - so, i would have to go with the 12" as a start.

I live in Northern New Jersey [Bergen County, literally 10 miles close to Manhattan, NYC]

Only known two factors:

1. zone 6
2. my local frost/freeze line is 18" [is there, based on the freezeline as an indicator, a way to determine or infer how many inches max to expect?]

I'll try to give you my spec's and you can tell me, if you can since you're a bit far away, what you think i will get.

we're looking at a pond:

1. 12 x 12
2. 5 shelves;
3. each shelf is 6" deeper then the last until you hit 30" dept;
4. shelves, basically, range from 16-20" in width.

From this, in the most extreme winter possible, how many inches of ice do you think that I would get on that size garden pond with a 3000 gph pump and airstone to keep a hole? This will tell me how safe it is to leave plants on the shelves - if its possible i would get 12", i will not leave them to potentially freeze on the first [6"] and second level [12"] shelves.

I think, like me, you can expect at most 10-12" in the worst winters. That is not every year, and it doesn't last the whole winter either. Most winters, my pond gets 6-8"of ice at the worst over winter with the 10" being a record for my pond. Also, bigger ponds may get less, ponds with more water movement may actually get more in the non-moving areas due to supercooling (but less ice in the moving areas), and there are other factors that vary location to location and pond to pond.

I don't know if the earth freeze line correlates to the water freeze line but probably so. Pond freeze lines are not as deep as earth freeze lines.

I would say that most winters, hardy marginals of most kinds would do fine on your deeper shelf. Only those that could freeze solid would do ok in the shallow shelf. You say that shelf is only 6" deep? Most pots are that high or higher so you want to add depth to take into account the depth of the pots. I think my 2 gallon pots are 8" deep so if you want a few inches over that, the shallow shelves would be 10-12" deep. But, if you're using pockets and the 6" is only over the pocket, that's fine. You've thrown out so many ideas that I'm a little confused.

for the type of pond im describing, 12 x 12 down to 30" appox.,

1.do you think i could ever get surprised by a freeze right to the bottom of my 18" shelf?

2.think i made a mistake: my freezeline for electic is 18" and i think its 36" for water pipes....

3. my pond for next year will be designed in levels of depth: 6", 12", 18", 24", 30", & maybe 36" - not sure on the widths.

4. since i never intend to use pots, except for the rush and cattails, i wont need to factor in pot or soil depth beyond the expectation of say 2" gravel and a few stones to hold roots down here and there. From all of the many, many, and many testimonies i've read and correspondenses, all marginals WILL do perfectly well in no soil, no fertilizer tablets, and just pond water - and done need, in theory, any substrate - but to hold them down. i wanna eliminate the pots, keep out the soil, and clear up the algea-feeding nutrients avaliable in teh pond water. The only thing is to consider whether i want to have lilies in soil pots or have them, also, in the gravel which will mean i need to fertilize them, as they will not do well, i bet, in a koi waste free pond as mine...

"1.do you think i could ever get surprised by a freeze right to the bottom of my 18" shelf?"

I doubt it.

"4. since i never intend to use pots, except for the rush and cattails, i wont need to factor in pot or soil depth beyond the expectation of say 2" gravel and a few stones to hold roots down here and there."

That's going to be the main thing, if the plant can be supported by a shallow substrate. For most, it shouldn't be a problem but a few like common cattails and hardy cannas, they may flop over.