It may take a month or so for any algae to show up in your tank but it can take a bit longer for the tank to become fully cycled, when i used ocean rock in the tanks i got an ammonia reading as something must of been dying off (who knows what) and this started my cycle off. If you dont get any ammonia readings in the first month you can always put in a fish flake or food pellet and let it rott down, this will provide ammonia and start the cycle.
The ammonia will shoot up and next the nitrites will shoot up sending the ammonia down, next the nitrates will start to creep up and the ammonia and nitrite readings will drop to zero, when that happens you should dump your shrimp and snails in strait away. Failing that you can just do small water changes to reduce any nasties if they crop up while you have shrimp and snails in the tank.
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