How to keep a stock water trough clean from algae

The short answer is frequency, not a product. Agriculture Victoria's guidance for stock containment areas is that surface material should be skimmed off the water daily, and that troughs should be completely emptied, cleaned and re-filled every 1 to 2 days. Everything else you do is about removing the conditions that let algae and sludge get started in the first place: warm, stagnant water, feed residue, dust and a trough that is awkward to drain.

What makes algae and sludge build up

Agriculture Victoria notes that animals in a containment area live in close proximity to each other, can be exposed to increased levels of dust and mud, and are often on a more targeted diet than they would get in the paddock. All three of those end up in the water. Evidence from recent droughts indicates stock avoid or reduce consumption of water that is warm, stagnant, polluted with food residues, or has dust or straw floating on the surface.

The cloudiness you can see has a name. Turbidity is caused by suspended clay, silt, fine organic matter and microscopic organisms, predominantly living algae. Highly turbid water is likely to have elevated levels of phosphorus, which Agriculture Victoria describes as a key factor in producing algal blooms. For scale, clear water measures about 1 NTU, slightly cloudy water about 10 NTU and very cloudy water greater than 50 NTU. To avoid sludge forming in pipes and tanks, the advice is to avoid using water with turbidity above 5 NTU.

Two design and siting factors make it worse. MLA's feedlot design manual points out that cattle drink soon after feeding and hold grain on their muzzles and in their mouth for a time, so a water trough placed close to the feed bunk gets more grain transferred into it and needs cleaning more often. Agriculture Victoria says the same thing in one line: locate troughs away from feeding areas to minimise water contamination. MLA also notes that the inside surface of a concrete trough gets harder to clean over time as it deteriorates through hardness of the water, cattle licking, saliva, enzymes in feed stuffs and mechanical cleaning.

What the guidance says to do

From Agriculture Victoria:

• Skim surface material off the water daily.
• Empty, clean and re-fill every 1 to 2 days.
• Keep the water level close to full at all times, which needs a sound supply and a protected float valve.
• Choose a long shallow trough with a smooth internal profile, a gate valve and a large outlet bung, because that makes cleaning quick and efficient.
• Sit the trough on a raised pad of gravel, stone or concrete for drainage and stability.
• If there is any question about the water itself, send a sample from the source to a water testing laboratory. The guidance asks for water that is fresh, cool and clean, low in salt, organic matter and suspended clay, and free of substances such as blue-green algae.

From MLA, on the mechanics: troughs are cleaned by flushing out the existing water and then adding more during scrubbing, so each trough wants a large drainage outlet positioned so the water flows away from the trough, preferably to a drain. Low volume troughs waste less water into the pen with each flush, and long, narrow, shallow troughs are preferred over large, deep, high volume circular ones. Rectangular troughs are more easily cleaned internally than circular ones. Surface coatings are best applied when the trough is new.

The practical options

1. Hand clean on a schedule. This is the baseline, and it works. Make it faster with a drain you can open quickly, such as the stand pipe MLA describes, which is unscrewed to open the discharge bung.
2. Fix the siting. Move the trough away from the feed area and onto a well drained pad. Shade over the trough reduces heat loading on the water, though MLA warns the ground around it stays wet longer and stock tend to congregate there.
3. Automate the flush. A trough that empties and refills itself on a schedule does the frequency part for you.

What the hand cleaning is costing

Work it out before you change anything. One trough cleaned five times a week, ten minutes a time, with your labour at $35 an hour, comes to about $1,517 a year, or about 43 hours a year for that one trough. Our calculator takes a minute and uses your numbers, not ours.

Where a self flushing trough fits

The SATURN trough opens a flush valve at an interval you set from your phone, water runs along the floor and carries sediment and feed residue out the drain, and the mechanical float valve refills it. Manufacturer figures: 50 litre trough volume, 2,225 mm long, approximately 60 litres per flush, one to two flushes a day depending on stock numbers, operating pressure 200 to 1,000 kPa (2 to 10 bar), battery life about 12 months, and installation in about 30 minutes. It does not replace checking the trough, and it does nothing about source water quality, so the 5 NTU rule and lab testing still apply.

What we recommend

Start with the guidance, because it costs nothing: skim daily, empty every 1 to 2 days, keep the trough full, and move it away from the feed. If that frequency is realistically not happening on your place, test a flushing trough on your own farm rather than taking anyone's word for it. Our 90 day trial in Victoria puts one beside your existing water with the pass marks agreed in writing first, and at the end you decide.