Thanks to everyone who responded.

I do have an inflow and outflow of water. It is supplied by a very
small underground spring and a wet weather tributary. The trib runs
about 6-9 months of the year and varies during non-raining periods
between 20-50K gallons per day. As such, my only real issues may occur
during the summer months when there is not pass-through water.

Do barley bales become 'used up' at some point? IE, what is their
useful life in controlling algae?

One thing to note on the gallon calculation. The pond is U shaped and
the cals listed do not account for the 3:1 banks. At most, I'll be in
the 2.5 M gallon range.

Be design, my full flood stage is over 15 M gallons. However, this
would only occur during a 100 year rain. I will probably never see it.
I have outflow culvert capacity (two 3-foot and two 4-foot) of about
10 million gallon per hour. During that rain, I am sure it will
destroy my pond by flushing the fish down stream....Of course, water
will be about 50 foot from my front door as the spillway is being
overran....I don't imagine I'll care about the fish at that point!!!!!

Thanks again!!!!