Oopsies!  Common Problems For Your Lotus
Aphids - These nasty little things are by far the most
common problem that we've encountered with our Lotuses
(its a Kane`ohe thing, not much of an issue elsewhere).  You
can usually find them on the stems and undersides of the
leaves.  Thankfully they're little more than an eyesore if
treated promptly.  There are a number of off-the-shelf
treatments for Aphids but at our nursery we exclusively use
Volk Oil to treat all our plants.  It's mostly non-toxic, it
mixes and applies easily, and so far it hasn't affected any of
our fish; including our goldfish which are extremely sensitive
to environmental toxins.
Curly Leaves -  This is the most common way in which the Lotus
shows that it is not happy, and could have several different causes:
1.        Your roots have dried out.  If this happens, the plant cannot
be saved.
2.        Your roots are boiled. Depending on severity, the plant may
be saved.  Take steps to lower the temperature at the roots.  
Something more permanent than ice is needed, try shading the
water or using a deeper pool.  Don’t forget that the pond container
itself might be fully exposed to sunlight and contributing to the
problem; that's the case with the top photo on the right.
3.        Someone or something has been fiddling with the roots.  
Unless you really know what you’re doing, it’s not a grand idea to go
poking about in the Lotus’ root structure during its peak growing
season.  They don’t like it.  If you have overly inquisitive fish in the
pond (such as Koi) you may wish to have a quiet word with them
about digging in your plants.
4.        You're not using enough fertilizer.  The plant in the bottom
photo is suffering from this.  Add some fertilizer and the plant will be
very happy with you!  
Pale Leaves - This is one
caused by overfertilizing,
which is very hard to do with
Lotuses.  Nothing you can do
about it if you do... stop
fertilizing for a while.
Slugs - Cory's Slug Bait,
spread liberally around your
pond, should clear this up.
There are other brands in the
same way there is other
mayonnaise besides Best
Foods; not worth it.   Don't put
any slug bait in your pond, it
will kill the fish.
Winter- Nothing's wrong,
the Lotus is a seasonal plant
and goes dormant for
Christmas.  Good time to
split it if you like, hold off
fertilizing until you see leaves
next year.  (Or see the entry
for 'Pale Leaves' on the left.)