Sara, try sand. Either masonry sand or play sand. Don't fertilize until they have at least 3-4 leaves.
Corrie

Thank you for the sand suggestion, I am going to give it a try. Will let you know how it turn out.

Sara, I hybridize waterlilies and sometimes lotus for fun.
Here's what I do for lotus.
Let the seeds dry until the outside is hard.
Rub one spot of the seed on fine sandpaper, concrete, whatever is handy, until I see the white inside layer.
Soak in warm water.
When they sprout
Take Dixie cups filled 1/2 with sand, stick sprouted seed in middle. top off with warm water.
Put in shade.
Don't fertilize until they have at least 3-4 leaves, floaters. I break pond tads up with a hammer and just use small pieces.

I lost a lot of them to rot when I tried any kind of dirt.

One problem you might be having right now is heat. Keep them in the shade or just morning sun this time of the year. Full day or afternoon sun can cook them.

HTH
Corrie

You know, Victoria Adventures has all types of info on starting lotus seeds. Just follow the link.

Here is a link that might be useful: Lotus cultivation

Corrie & pndmanial, thank you for the info! Hopefully, my lotus seeds will survive in sand.

Just an update about my 2 lotus seeds -- they are doing great!

Corrie, I followed your advice and used sand. I put one seed in a 3" diameter plastic container and the other in a 6" diameter plastic container, fill both containers with 3" sand. And put both containers into a dishpan and filled the dishpan with water, 2-3" above the sand. Amazingly, the water in dishpan has stayed clear and clean all this time.

To avoid lotus being baked, I kept them indoor near a sunny window (air conditioner vent closed off in that room). And when each seed has 4 floating leaves, I put in a little fertilizer(small pieces of aquatic plant food). Now the seed in small container has 5 leaves, the one in bigger container is trying to grow the 5th leave.

I have never gone this far in my previous attemps and am just thrilled with the result so far.

So what's my next step? How often should I fertilize them? How long do I keep them in these small containers? I am sure there is a point that I need to put them into a bigger container, but exactly when I am not sure.

Anyway, this is where I am now and thank you so much for the advices, please keep them coming!