I’ve grown lotuses for many years, though mainly from rhizome sections instead of seed.
As long as the pond doesn’t freeze solid, the lotus will be fine. If you plant it directly on the bottom, it will take over the entire thing in one growing season. You will get more flowers that way. I would plant out the seedlings in buckets (individually; you only need one to fill the pond, keep any others as backups) when it has a few leaves, wait until it has filled the bucket, and plant it out in the pond when water temperatures are consistently in the upper 60s-70s. Warmth is important. If the water isn’t warm enough, the plant will have trouble establishing. In my experience, they aren’t too bothered by cool nights (high 40s-50s) early in the season as long as it warms up considerably during the daytime.
I don’t know if you are able to control the water level in the pond, but when I start lotuses I usually add just enough water to cover the growing point by a few inches. The first leaves will float on the surface and have some capacity to elongate with changing water levels, but I wouldn’t try to test that, especially with a seedling. As leaves form, I gradually increase the water level until the container is full. Lotuses don’t need deep water. 4-5 inches is enough. The amount of soil is more important.
Raccoons will definitely pull and eat lotuses. I have lost many newly planted tubers over the years. I will usually put a sheet of wire mesh over the entire container and weigh or pin it down until the plant is well rooted and there are multiple leaves. Usually at that point they are more difficult for raccoons to pull out, but I have had raccoons decide to go for a swim in my lotus tubs and tear up all the leaves.
Lotuses are heavy feeders, but can be damaged by fertilizing too early. Don’t apply any chemical fertilizers until the first above-water leaves appear. I have had good results with 3-4 inches of composted cow manure topped with 12-18 inches of topsoil. There’s no need to mix in the manure. The lotus will find it as the rhizome explores the container. I follow up with waterlily/lotus fertilizer every couple of weeks once flowering starts.
It’s best to think of the growth pattern of a lotus like Bermuda grass or bearded iris. Most of the growth occurs from a single growing tip, which will extend for many feet if allowed. Periodically, a new growth point will branch off, but prior to that, damage to the growing tip will likely kill the lotus. If you’ve seen lotus “roots” (actually rhizomes), the joints between the fleshy sections are the nodes where you’ll have a leaf, the actual roots, and an axillary bud, Flowers and new growth points arise from the axillary bud where the leaf attaches to the node. Some varieties will flower with every emergent (non-floating) leaf, others are less floriferous. Since flowers only occur at leaf axils, the rhizome needs to keep growing to produce more nodes and subsequently flowers. They’re perfectly content to grow in circles around the edge of a tub, however, as long as their nutrient needs are met.
Sun is important. They need at least 6 or 7 hours of full sun exposure to grow and bloom well. Don’t underestimate the amount of water they transpire as they grow. They can take summer temps in the low 100s for weeks at a time but will suck up enormous amounts of water, so make sure to keep an eye on the water level.
It’s important that you don’t plant lotuses in containers with sharp corners, as the growing tip can get stuck there and die.
If you’re growing them for seed production, you will want to hand-pollinate the flowers unless you have a lot of carpenter and bumble bees around. Honeybees seem too small to be very effective pollinators in my experience. Most flowers will last three or four days. The stigma is receptive for the first two days while pollen is shed on the second and third days. I generally harvest the seeds when they are fully grown but before they turn brown. Once the seed coat hardens, it’s very difficult to shell them.
For root production, there are varieties bred specifically for that available. The roots/rhizomes/tubers/whatever you want to call them of regular varieties tend to be fairly small and fibrous. The varieties for root production devote most of their energy towards vegetative growth and flower minimally, if at all. Unless you have a fairly large pond, its unlikely you will get enough of a harvest to be worth it. I grew one of these once, and the harvest process isn’t really something I care to repeat again.
Sorry for the rambly post. Hope this helps and let me know if you have any further questions.