July 13, 2011

Green Water / pH Crash?

Today's Pond Q&A

In this issue:

- Green Water

- pH Crash?


Question #1>

Hi Carolyn,

Help!! I have a Fish pond made of cement blocks, about 3-4 feet
deep and about 6-7 feet long a good size. I have had it several

The problem -- GREEN WATER. I fight this every year, I have lots of
fish and they thrive having babies now, but GREEN . . .

Is there anything that I can do to clear some of this yuk up other
than purchase a UV light system??

I love sitting and watching the fish when they come right to the
top. I'd like to be able to look down and see them.

I clean my filter every other day again yuk slimy pea soup. I hope
you can help.



Answer #1>

Hi Margaret,

If this were the type of algae we call "pea soup" it wouldn't be
clogging the filter, nor is it slimy. So, I suspect you have one
of the filamentous forms, or a combination of algae types.

Algae loves hard water and high pH. It also thrives on fish waste,
sun, phosphates. I'm not sure if a UV is the answer. You might
try it, but if it is filamentous algae, it won't help.

The more fish in there, the more algae you will have. Are you
doing weekly 25% water changes to remove phosphates? That would
really help. What else would be a big help would be to thin the
herd. You didn't say how many fish you have, or how much/how often
you feed them, but too many fish can be as little as one too many
and the entire system goes haywire.

You can use Barley Straw Pellets or Barley Straw Concentrated
Extract to help bind the nutrients that algae feed upon.

So, if you want less algae and better view of the fish, you
should monitor the fish load, feed sparingly, use Barley straw and
do the 25% weekly water changes. If that doesn't clear it up, you
still can get a UV light.




Question #2>

Hi Carolyn,

All my fish died overnight. Yesterday they weren't eating and
seemed very lethargic ... (5 fish in my little-bitty small 60 gal.
pond) ... two were 6" koi, 2 4" fan tail goldfish and 1 2" koi
that I got 3 months ago. The 4 big guys survived the winter.

I tested the water as I was pulling out the carnage ... and it
looks like the pH crashed - plants cover only about 40% of the
surface and they are doing well. There are several snails in
there too - but I noticed yesterday morning that the pond seemed be
getting 'dirtier' than usual.

My question is, are the snails probably dead too? I don't see any
of them and they were seldom active enough to see if they are
alive or not. I thought I read somewhere that snails would die
off first if the ph started to crash as a warning. (I wouldn't be
heart broken if they were just gone) They never got my water quite
clean enough to see them often enough. I have a UV filter that
did great a first but I never really got that crystal clear water
that I was hoping for. I put in an airstone just yesterday (after
they looked kind of weak).

Would it be a bad move to put new fish in right away? How long
should I wait?

I know I was negligent in not testing my water enough ... last
summer I was testing religiously ... this summer the fish seemed so
happy and healthy that it didn't seem necessary.

I know my pond is small ... but it's been pretty stable for 3 of
the 5 years that I've had it. This is the first time all the fish
have died overnight in 2 years.

Any advice for the 'really really' small pond owners out there -
there might be a couple of us still.

Thank you


Answer #2>

Hi, Kathi,

I think the same advice that is given to large pond owners would be
good for small owners- do lots of water changes, do not overstock
and do not overfeed.

In your case, you were terribly overstocked, especially considering
you had koi in there. Every year, in fact each month, koi are
growing larger, even in confined quarters. It is a fallacy that
all fish grow to the size of the container.

Last fall I "adopted" five huge koi and six or seven overgrown
goldfish from a very small preformed pond in someone's backyard.
The water was amazingly clear and the fish were, as stated, nothing
less than huge. I can't see how they were able to turn around in
there. The largest fish was 37".

I never saw the previous owner do it, but I can tell you he was
doing a lot of water changes and very careful feeding for the fish
to all survive and thrive for 14 years in that small environment.
He said the pond contained 400 gallons.

In your case, it is quite likely your fish died of ammonia
poisoning. Yes, it could have been a pH crash, but was the pond
really that dirty? Every year you should have taken the pond apart
and given it a thorough cleaning. It seems odd that you had the
fish and pond for 5 years and suddenly the pH crashed if you were
maintaining it properly. The signs of pH crash are that the fish
turn white and die quite rapidly.

As for waiting to put new fish in? I would say a good thorough
cleaning and consider it a lesson learned. No koi in 60 gallons of
water, a good filter, weekly water changes and careful feeding
regimen will have a nice pond up and running for you.


========== @SK Carolyn =================
Have a pond question? Just send it in
to: Carolyn@macarthurwatergardens.com
and our own in-house pond expert will
try and answer it for you! Write POND
in the subject line for quick response!

Happy Pondkeeping!

Brett Fogle
MacArthur Water Gardens

MacArthur Water Gardens
PO Box 3628
Alpharetta, GA 30023-3628

Posted by bfogle at July 13, 2011 11:07 PM

This is to answer the question re: herons from July 12. I am unable to get into the questions any other way as Carolyn's site will not bring work. I have a tip for stopping herons from getting into the pond:Blackberry branches! Someone mentioned a solution to the same heron problem I was having. She said to put piled blackberry branches (dried) where the heron was standing to get into the pond. I put quite a few branches that have dried in the sun around the areas that a heron would need to stand in order to get the fish. Results: great. Not one fish has been taken. I guess they don't like standing on blackberry thorns anymore than we do.


Posted by: Susan at July 20, 2011 03:57 PM