Question
QUESTION: I have a very small pond about 8 cubic feet. Since we moved in about 3 three years ago there have always been frogs, tadpoles and healthy plant life. Over the last month the frogs (we saw as many as 8 at one time) and tadpoles seem to have disappeared. In addition clouds of very tiny (less than pin-head size)creatures have arrived and seem more prolific. Now the water lily leaves are being eaten or are dying, going black and rotting. What should we do and what is wrong? We have fresh barley straw in the pond (3 weeks old)

ANSWER: My preliminary guess is that the continued presence of frogs has driven the ammonia level up.  Frogs do their business in the pond, which produces ammonia.  The ammonia gradually drives the pH down.  The plants are fine with excess ammonia; but once the pH is affected, the plant life suffers.

Those little creatures could be a one of many different things.  It seems as if they are insect in nature, and may be eating the lilies.  Often times, insects will choose partially deteriorating plants as they are easier to chew.  It may be aphids, but could also be a number of things.

Do you have any fish?  Update me after testing ammonia and pH if you are still having problems.  A 50% water change may help things along.  You also could benefit from testing the alkalinity of your water source (whichever one you would use to re-fill the pond).

---------- FOLLOW-UP ----------

QUESTION: Thanks for the advice. I don't have any fish. How do I check
the ammonia/pH levels? Is there a kit available? There is
also a very large number of water snails, and they seem to
be increasing by the day, but appear to have eaten a lot of
the algae on the liner. Should I try to clear out some of
the sludge at the bottom of the pond or will a 50% water
change  be adequate?

Answer
There are kits to test water parameters.  Each one should be less than nine dollars.  Some pet stores also test for free, or for a small fee.

To be honest, what you should do depends entirely on your goals for this water feature.  If you just want clean, clear water you should do a complete cleaning of everything and add chlorine bleach to the water every week or so.  If you want plants and clean water, you could do a 50% water change (skip the chlorine) and get some new plants.  If you want fish, there's a whole lot of work to do.  If you just want frogs, you're going to need a large filter to handle the amount of waste they produce.  You could also fill it in with dirt, and never have to bother with it again.

Some people enjoy the benefits of having snails in the pond and some people hate the fact that the snails don't stay confined to the pond, making yard work more difficult.

If this were my pond, I would empty it out entirely of every speck of anything that wasn't plumbing-related.  Then re-fill and de-chlorinate.  Then add new plants and start from scratch.

There is a lot of 'science homework' involved in owning a beautiful, healthy water feature.  By deciding what you want out of this feature, you will more easily be able to determine your course of action.