The G Man wrote:

Am fairly new to looking after ponds.... Anyway, have a pond in our back
garden. It's quite a small one (only holds around 110 litres of water)
but enough for a small fountain, some pond plants and maybe (if I can
get the environment right) a few small fish. But for now I'd just
settle for a clean pond.....

110 liters is pretty small for goldfish, but fine for a few _small_ fish.

The water is pea green.. Have tried Interpet Green Away & sludge buster
for nearly a month now without any noticeable improvement

That's part of your problem. Chemical solutions rarely solve the real
problem - in your case too many nutrients for the algae

- have set up
my own DIY filter (a skippy up flow filter) which has been running 24/7
for about two weeks now and spiked it with plenty of good bacteria.

That's a good start, but not knowing where you are, I can't say whether
there's any hope that a bio-filter would be having much success yet. It
takes many weeks if the weather's still cool, and spiking it with bacteria
may or may not speed it up.

Have tested the water using test strips to check for nitrate/nitrite/ph
level etc but everything seems within the levels stated for a healthy
pond.

I would guess so. Though you really should quote numbers - it's amazing how
often people tell us that some very small number for nitrite/ammonia is
"acceptable". However, you don't have fish so nitrite is completely
unimportant.

Have got several pond plants growing in an old washing up bowl ready to
be put in the pond but I want ensure that the water is safe for them
first. I put some in last year and they died within a few weeks.

Huh? You don't have _any_ plants in the water, and you want to get rid of
the algae first? Put the plants in there and forget about the horrible
chemicals! The plants are the only way to control the algae (as long as
you're not going to resort to a UV sterilizer).

Anacharis, hornwort, water cress (especially the water cress, because it's
really cheap) are the way to get started on cleaning it up.
--
derek