Four Batches, Four Ratios: Coco Fibre Against Gel by Volume

Four 20 litre tubs, four ratios by volume: 4:1, 3:1, 2:1 and 1:1 coco fibre to hydrated gel. Same brand of fibre, same powder, same water, same room at 21 C, one hygrometer each, 30 cm above the substrate and out of the misting path. Five weeks, one misting of 20 seconds every second day.

The question was simple: where is the point at which more gel stops helping? The answer took three weeks to appear and was not the ratio I expected.

How the batches were built

Each tub got 6 cm of mix over a 3 cm drainage layer of clay balls, with a mesh barrier. Gel was hydrated at 1:150 in the same tap water and drained for ten minutes before measuring. Fibre was hydrated to field capacity first, then the gel was folded in, not stirred hard, because hard mixing crushes the gel into paste and changes the result.

That last point matters more than any ratio. Two batches at the same numbers will behave differently if one was folded and one was beaten. If you take one thing from this, take the folding.

What the numbers say

Every step up in gel bought humidity, and every step up in gel bought mould sooner. The 1:1 mix held 88 percent at day five, which looks like the winner until you see it had already bloomed on day 12 and had sagged 3 cm by week five. A layer that sags is a layer that has lost its air structure, and a layer with no air structure is a layer that moulds.

The 3:1 mix is the compromise the table points to: 84 percent at day three, 79 at day five, no mould for a month, and minimal settling. Not the wettest, and the one I would build with.

The counter-intuitive finding

The 4:1 mix, the driest, was the only one that never moulded and the only one where the surface stayed crumbly to the touch at five weeks. It also held 68 percent at day five, which is too dry for most dart frogs but perfectly reasonable for many salamanders and for a grow-out tub.

So the interesting result is not “3:1 is best”. It is that the dry end stayed biologically stable while the wet end went off. If you are fighting mould, the fastest fix is usually to move one step drier, not to add another product.

There is a second reading of the same data. The gap between day three and day five is the useful measure of a mix, not the day-three number. The 3:1 batch lost 5 points over two days; the 1:1 lost 3. A mix that barely moves is holding water in reserve. A mix that starts high and falls fast was never holding much, it was just wet.

Building the 3:1 mix

• 20 litre batch: 12 litres of hydrated coco fibre, 4 litres of drained gel, 4 litres of fine bark or leaf crumb.
• Fold the gel in with a flat hand or a spatula; do not use a drill mixer.
• Pack in 4 cm lifts, firm but not compressed.
• Rehydrate the surface with a spray, never by pouring; pouring collapses the structure at the point of impact.
• Replace the top 2 cm every 8 to 12 weeks rather than turning the whole layer.

Fibre quality varies a lot between suppliers, and a batch that is dust-heavy will hold less air than a coarse one at the same weight. If your fibre looks like coffee grounds, go one step drier on the ratio to compensate. The polymer powder mixing ratios you see published assume a fairly coarse fibre, and that assumption is worth checking before you copy a number.

Run your own four

You do not need a lab. Four 5 litre tubs, one hygrometer each, and a note of the day you first see fuzz will give you a house answer in five weeks. Keep the fibre and water constant and change one thing.

Mix a 3:1 batch this week, keep a 4:1 alongside it, and see which one your species actually uses. The animal will choose, and its choice is better data than any table.