Barley Straw "Natural" Compound Used - Risks ?

[Sauce]

OK, So I have dosed my pond with a Barley Straw "Natural" Compound . Then I decided to check up on exactly what the risks were on here ! OMG , Now I'm worried
I'm thinking its the same as a normal algicide or is it something different and ok ie carries a lower risk ?

I followed the instructions, added the correct amount into a bucket of pond water first, evenly added it and have left my 2nd waterfeature going, as its a waterblade and its agitates the water alot.

What should I be on the lookout for - danger signs ? How long after adding should I expect the algae to start breaking down and contaminating the water , reducing o2 ?

Background:
My Pond has had a massive outbreak of stringy algae this week. Every surface is covered and it looks horrible.
As I'm having a big BBQ and get together with friends in 4 days time, I needed it fixed fast ! Bring on the quick chemical fixes !

At first I thought it was overfeeding ( as I was away and had a houseguest feeding for the week) but I got him to show me how much was being used, and it was ok.

I had also added significant fish numbers (50 inches of koi) 2 weeks before and thought I had a cycling problem.
Pond is 1486 gallons, with a 2000 gallon per hour pump and pressure filter.
Tested the waters and everything is good on Day 1 of treatment , no detectable levels of Ammonia, Nitrites or Nitrates.

PH was 7.5, but after the Barley Straw was added, its now 7.0 I'll measure it again in the morning - perhaps a water change if it drops below 7 ?
My pond is all rainwater, so its all soft water, which I think means the PH can lower if you dont clean out the sludge as it forms ?

I have one 24/7 waterfall, and I'm thinking this doesn't make enough O2 for the fishies, as they wont go up the other end of the pond, they always stay up the end with the waterfall. I cant leave my waterblade going all the time as its a bit noisy and I don't want to risk upsetting the neighbours, but it certainly mixes up the other end of the pond pretty good.

Lastly I'm suspicious about extra sunlight, We have had a good solid 4-5 bright sunny days in a row, spring is very late this year for us, would this be enough to cause a bloom, as my pond gets 80% sun.

I'm able to easily perform water changes if fish look like they are in distress and have rainwater on standby to add from the storage tank, but dont want to purge too early.

 

[Meyer Jordan]

Barley in any of its available forms only has effect on certain species of algae. I do not believe that string algae is one of them. Barley,as it decomposes, releases an acid into the pond that can and will, in sufficient quantity, lower pH. It also releases tannins into the water column which will affect Oxygen levels by inhibiting photosynthesis in any submerges plant or algae.
String algae is typically a sign of excess Phosphorus.
Other than natural removal, there are no quick fixes for String algae, especially if it is submerged.
I would also suggest that you have too high of a fish load for you present system and this will only become more troublesome as these fish grow.

 

[IPA]

@Sauce , I suggest you test your KH, like ASAP. Short of that you could probably, (probably but w/o a test no way to know) safely add 1/2 cup of baking soda to the water.

 

[Sauce]

Ill get a phosphorus test kit tomorrow. As my pond isn't cycling, and has no detectable Nitrates, I assumed it wasn't a plant fertilizer issue.
Also as its in full sun most of the day, i'm going to look into putting some shade cloth over the top, as our summers are brutal here in OZ.
Unfortunate about adding barley extract then, waste of time ... what I read seemed to indicate it was a fix.

 

[Sauce]

@IPA You are that worried about low PH levels ?
I'll take action if it drops below 7 ?
If there is no Baking Soda in the house( its 12:30am atm) I can do a water change easily enough. ( Lets hope Meyer didn't hear that )

 

[IPA]

Ill get a phosphorus test kit tomorrow. As my pond isn't cycling, and has no detectable Nitrates, I assumed it wasn't a plant fertilizer issue.
Also as its in full sun most of the day, i'm going to look into putting some shade cloth over the top, as our summers are brutal here in OZ.
Unfortunate about adding barley extract then, waste of time ... what I read seemed to indicate it was a fix.

Lack of KH can lead to PH crashes and all the "bio-load" uses it. It is also important in cycling a tank as the bacteria use calcium carbonate (unsure exact carbonate used) lowering the KH as it is used. Rain water provides very little in the way of hardness.
Barley extract is good a clearing green water algae, the string stuff is just a natural cycle your pond needs to go through. Adding plants like iris, most marginal plants, helps to remove the "waste" that algae feeds on. I believe string algae is one of the most basic and why it gets going so well before the beneficial algae takes hold. Best just to pull it out with a bristle brush or your hands.

 

[Jhn]

Just to add, your getting no readings on your water parameters because the string algae is consuming it. The reason you had a string algae explosion is because of the recently added fish load. Ideally, more plans in the pond whether it be marginals, floating or submerged to starve the algae of nutrients. Dumping quick fixes into your pond is a good way to end up with a mess on your hands.

Sunlight in and of itself isn't the issue. Most of my 8000 gal. pond gets sun roughly 10 hours a day, I have no algae issues at any time during the year. Why? Because I have plant covering probably 60% of the pond. Patience, the algae will go away and if done right ( source of the problem tackled i.e. Excess nutrients ) will stay that way.