White Jelly Bumps on Mopani Wood: What They Are and Why You Don’t Need to Restart

ByThe Answerlode Editorial Team

What Are Those White Jelly Bumps on Your Mopani Wood?

Those soft, clear-to-white bumpy growths on your Mopani wood are saprolegnia, a filamentous fungus. It’s normal, temporary, and completely harmless to your tank and any future fish.

When you submerge fresh driftwood—especially dense, organic-rich wood like Mopani—it leaches sugars, cellulose, and other compounds into the water. These compounds feed fungal and bacterial colonies that form on the wood’s surface. What you’re seeing is the fungus doing exactly what it’s supposed to do: breaking down the wood and consuming those released organics.

Why It Looks Like Jelly

The jelly-like texture comes from the wet biofilm matrix. The fungus creates a slimy coating that can appear cottony, gelatinous, or bumpy depending on how thick it grows and the angle you’re viewing it from. The faint orange or brown tint you noticed is common—it’s often just tannins from the wood mixing with the biofilm.

This is not a sign of contamination or tank failure.

The Timeline: When Will It Go Away?

In most cases, saprolegnia fungal growth lasts 2–4 weeks. As the fungus consumes the available organic compounds, it starves and recedes. Simultaneously, bacterial biofilm begins to colonize the wood surface, which is even healthier for your tank ecosystem.

Some aquarists report it taking up to 8–12 weeks, especially on heavily used Mopani pieces with lots of surface area. Patience is key.

Should You Remove It?

You don’t have to. The fungus isn’t harmful and leaving it alone lets your tank’s natural ecosystem establish itself. However, you have options:

  • Let it disappear naturally. This is the easiest path and signals that your tank is developing a healthy microbial balance.
  • Manual removal. You can gently scrub the wood with a soft brush under running water. It will likely return, but many aquarists do this for aesthetic reasons.
  • Biological control. Adding algae-eating fish, Amano shrimp, or certain snail species (like nerites) will accelerate the process—they eagerly eat the biofilm.

Avoid harsh chemicals or aggressive scrubbing, which can damage the biofilm layer before beneficial bacteria establish themselves.

Why API Proper pH Doesn’t Cause This

You mentioned adding API Proper pH 7.0 just before the growth appeared. This is coincidental timing, not the cause. pH buffers don’t trigger fungal growth. The fungus was almost certainly already colonizing the wood—it just became visually obvious after you noticed it a few days later.

When Can You Add Fish?

You can add fish now if your tank is cycled. The fungal growth poses no threat to fish, shrimp, or invertebrates. In fact, the biofilm becomes a food source for bottom-feeders and grazers. Healthy fish won’t touch the wood itself; they’ll eat the microorganisms on it.

The only reason to wait is if your nitrogen cycle isn’t complete—but that’s separate from the fungal growth you’re seeing.

What About Tannins?

Mopani is notorious for releasing tannins, which yellow or brown the water. This is distinct from the fungal jelly you’re seeing. Seachem Purigen is an excellent tool for managing tannins, though with Mopani you may always need occasional treatment. Tannins are harmless—they actually benefit some fish species and shrimp by softening the water and lowering pH—but if you prefer crystal-clear water, activated carbon and regular Purigen use will help.

Bottom Line

Your tank is fine. The wood is fine. In a few weeks, the fungal growth will vanish and be replaced by a more balanced bacterial biofilm. Your tank will then be ready for fish. There’s no need to restart anything. This is part of the normal setup process for any tank with fresh driftwood, especially Mopani.

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