Seachem PhosGuard

• Bead-shaped alumina media – spherical form keeps flow even through a reactor or media bag, instead of channelling around a clump of dust.
• Binds phosphate and silicate together – one media handles both of the nutrients that drive nuisance algae and diatoms.
• 0.87 mg phosphate per gram – the working capacity Seachem publishes for PhosGuard's alumina base.
• Fresh and marine safe – the same media works across both water types, at different dose rates (see Directions).
• Continuous or intermittent use – leave it running, or dose it in bursts ahead of a livestock introduction or a coral colouring push.

Freshwater volumes treated are roughly double the saltwater figures above, since PhosGuard is dosed lighter in freshwater. The litres above use the saltwater dose, the more conservative of the two.

• Suitable for: reef and FOWLR marine tanks, planted and community freshwater tanks, and any system where tap water or feeding is pushing phosphate or silicate up.
• Not suitable for: freshwater aquariums dosed with a phosphate-based pH buffer – PhosGuard will strip the buffer itself, not just the excess nutrient. Not a substitute for regular water changes or export via protein skimming.

• Pre-wet by adding the media to roughly double its volume of fresh water and rinsing before use – it can generate a little heat on first contact with water, which is normal.
• Position it in flow without letting it tumble: a reactor, canister filter media basket, or a filter bag in a high-flow trickle area all work. Tumbling grinds the beads and shortens their working life.
• Leave in place for around 4 days, then test phosphate and silicate. If levels haven't dropped to roughly 0.02 mg/L, the media is exhausted and it's time to replace it; if levels are still falling, leave it running.
• Can be run continuously or in short bursts, depending on how hard you're chasing a number.

PhosGuard can generate mild heat on first contact with water during pre-wetting – this is expected, not a fault. It is not a medication and carries no livestock warnings beyond the phosphate-buffer note above.

• A phosphate and silicate test kit – to know when the media is exhausted rather than guessing on a calendar.
• A media reactor or filter bag – for the even flow the beads need to work without tumbling.
• Seachem PhosNet – a higher-capacity synthetic GFO alternative where a smaller footprint or heavier phosphate load is the priority.

Covered by Seachem's standard quality guarantee in addition to your rights under Australian Consumer Law. Standard shipping applies to all pack sizes; no cold chain or dangerous goods handling required.

How long does one dose of PhosGuard last?

There's no fixed timeframe – it depends on how much phosphate and silicate is entering the tank. Start checking at around 4 days and replace once test readings stop dropping.

Can I run PhosGuard and carbon in the same reactor?

Yes, though many aquarists run them in separate chambers or bags so each media gets even flow rather than competing for contact time.

Will PhosGuard affect my freshwater pH buffer?

If your buffer is phosphate-based, yes – PhosGuard will strip it along with any excess phosphate. That's why it's not recommended for phosphate-buffered freshwater setups.

Is PhosGuard reef safe?

Yes, it's widely used in reef tanks specifically to keep phosphate and silicate low for coral colour and to limit nuisance algae.

Do I need a reactor, or can I just drop it in the filter?

A reactor or filter bag in a high-flow area both work. What matters is that the media sits in flow without tumbling – loose in an open sump is the one placement to avoid.