Backyard Aquaponics
A place to discuss aquaponics

Because pond algae are plants they both exhale and inhale oxygen in the photosynthesis process. Algae produce carbon dioxide during darkness and produce oxygen during daylight. The production of carbon dioxide can effect pH of the pond water considerably
pH and carbon dioxide... Carbon dioxide dissolves in water to form carbonic acid that has a pH of less than 7 so pH will tend to fall when carbon dioxide is high. This is what happens during the night with a reversal during daylight hours.

There is some quite complex chemistry involved here which I will ignore save to point out that when pond water pH levels fall below 7 then the potential for carbon dioxide problems increases. Pond pH should ideally be around 7.5 to 8.

Aeration of ponds

Aeration of pond water achieves two things both of which are very good for pond water and the fish:

Oxygen levels increase

Carbon dioxide is "blown" out of the water and this tends to push up pH levels.

Aeration also protects against those algae blooms and their dying - when they die they rot and release carbon dioxide by using up the oxygen resource in the water.

In summary it is difficult to over-aerate a pond and aeration has all round advantages in a pond and especially one with algae. The downside is the cost of a special aerating pump. All top koi keepers' ponds bubble with air as do their filters.

Deeper ponds without waterfalls and/or fountains as the means of creating circulation or mixing during calm periods also could be more prone to carbon dioxide problems.

Aeration and water mixing (waterfalls) are the MOST effective methods of controlling potential carbon dioxide problems.

Dissolved oxygen is also critical in solving algae problems the natural way using barley straw as will be discussed later.

Do not get carried away but DO beware of algae blooms (green or brown cloudy water) especially in summer and especially during calm periods and when there is no waterfall, fountain or aeration.

Remember the best way to prevent algae blooms is by UV light.

I use colloidal silver to treat cuts and burns. It works better than anything to stop infections and speed healing. Best part, you can make it your self! The high voltage setup makes much finer particle size and is more effective, but not required.

The way I see it the amount of algae is the problem with pH and O2 swings. Not a lot is required for tilapia. So, my theory is that CO2 production is not going to be a problem at lower concentrations of algae. This will, of course, have to be proven or disproved. Sounds like my next test project for this summer.

The other method might be growing algae in a separate tank and pumping that water across an angle bed sheet. The algae should build up on the sheet. It could then be scraped off and dried. Mmm that sounds like the most trouble free method. Either way, light must be limited to the fish tank.

Regarding DO levels. Far less problematic in fish grow-out ponds as the Asians do. They don't seem to be sweating it. Going to look further into what they say. Oxygenation at night via flow-forms and waterfalls might be a simple solution.

Algae and barley straw in garden ponds

Over the last 4 years or so barley straw has come into vogue as a means for solving suspended algae problems in ponds and particularly blanketweed algae problems. However discussion was almost always superficial, word of mouth or anecdotal.

Impact Upon Other Plants

Barley straw has not been recorded as having any undesirable effects on plants, fish or any other life in the pond. In fact quite the opposite has been reported. As algae growth diminished and other plant life improved this, in turn, created better conditions for insects and small crustaceans ... in fact the whole food chain showed benefits.

How Much Straw Is Needed Starting With A Clear Pond Early In Spring?

Algae grow near the surface where the sun shines brightest. As such it is the surface area of the pond that determines the amount of straw needed and not the volume or mass of water in the system. Dr Newman determined the following application rates for ponds:

Initial Application:

50 gms of straw per sq metre of surface (about 2 ozs per 10 square feet)

In muddy water double this level.

It is better to over-use the straw than under-use but within reason bearing in mind the oxygen requirement and that you need to prevent anaerobic conditions.

Additional Applications:

Reduce by a half until a level equal to about 10 gms per sq metre (half an ounce per sq, yard) is reached to maintain ongoing control. Any re-appearance of algae should result in increasing the dosage to previously successful levels.

Beware Dense Algae Blooms and Hot Weather

Both of these conditions are bad for oxygen levels in water as described in detail earlier. Avoid using barley straw under these circumstances unless extra air is in use.

New solution to blanketweed problems

Adding Fresh Straw

Do not go and immediately replace old straw with new ... rather add new straw some weeks before it is time to throw out the old straw. In this way continuous biological activity is maintained and the algae will not so easily regain a foothold. Remember the algae is under control ... it has not disappeared.

Take note as mentioned in the beginning that at higher temperatures the straw would not last as long as in colder water. Make an assumption that it will take about 1 month for activity to start.

It will not help to place straw on pads of blanketweed floating on the surface. The blanketweed must be removed first. Keep removing it regularly to maintain effective hydrogen peroxide levels in the water.

What exactly do you mean by an angle bed sheet DDM?

Cyara

"Not interested in the UV light option .... bad for fish.....but seems that a waterfall/fountain/flow-form is essential."

The first comment is simply untrue. The second, aside from aeration generates large amounts of negative ions in the air, good for you (brain releases seratonin) good for plants imho.

A bed sheet or other fine screen type material. The idea would be to pump water across it and let the algae in the water build up on the sheet or even to grow the algae on the sheet.