When to Replace Active Substrate (And How to Do It Without Losing Your Colony)

Active substrates like ADA Amazonia, Fluval Stratum, and UNS Controsoil help buffer pH and maintain soft water — but they don’t last forever. When they wear out, your pH rises, shrimp struggle to molt, and algae takes over. Here’s how to know when it’s time to replace your substrate and how to do it safely.

⏳ How Long Does Active Substrate Last?

• Lightly stocked tanks: ~12 months
• Heavy bio-load: ~8–10 months
• With CO₂ injection: 6–8 months
• Signs of failure: pH creeping above 6.8, KH increases, shrimp stress

🔍 Signs It’s Time to Replace Substrate

• pH rises to 7.0 or higher even with RO + GH-only remineralizer
• KH rises above 1 dKH
• Shrimp stop breeding or show molting issues
• Algae becomes harder to control

🛠️ Safe Methods to Replace Substrate

• Option 1: Full Swap
  Remove shrimp to holding tank, remove plants, siphon out substrate, rinse tank, and replace with fresh buffering substrate. Recycle fully before adding livestock back.
• Option 2: Half-and-Half
  Remove one half of the substrate, replace with new soil, wait 1–2 weeks, then replace the other half. Helps preserve biofilm and bacteria.
• Option 3: Thin Top-Up
  Add a thin 0.5″ layer of new substrate on top of old. Not as effective long-term, but useful if colony is sensitive to disturbance.

💧 How to Prepare New Substrate

• Rinse lightly if recommended (don’t remove all buffering particles)
• Pre-cycle new substrate in a small tank or bucket if possible
• Use Seachem Prime or Fritz Complete to detox ammonia spikes
• Test daily for ammonia, nitrite, and pH drift

🔗 Related Shrimp-Safe Tank Maintenance Guides

• Why Is My pH Rising?
• Remineralizing RO Water for Shrimp
• Shrimp Care Hub

Need help planning your substrate swap? Drop your tank size and current water parameters in the comments and I’ll help you step-by-step.