Substrate & Cycling Advice?

[Brennos]

How much of the good bacteria is in the substrate? I ask as, fingers crossed the issues with sick and dying fish in my tank is over, and I'm looking at re stocking slowly, over the next 2 months or so, I would like a few Kuhli loaches, but everything I read tells me they would prefer sand over gravel, which is fine, but I am weary of replacing my gravel, as the tank has only been cycled for 2 months, and the filter has only been on this tank for 2 weeks (Filter media is 2 months old, I transferred it to the external canister I have now). I wont be adding any more fish for at least 2 weeks, and then it will only be a single Gourami, then 2 weeks after that, I will add 2 more gouramis, then 2 weeks I will add 3-4 Loaches, I have decided on this method, as to not overload the filter etc.

So If I replace my gravel with sand this weekend, will that cause an ammonia spike, or any detrimental effects to the cycle in the tank?

[si_sphinx]

There is heaps bacteria in the gravel but it should be fine as you have your existing filter media and you arn't going to be overloading the tank with fish.

[smidey]

i suspect that the substrate does far more good than the bacteria in a filter, i have always started fresh tanks with existing substrate from another tank, added fish the following day & had no losses. i know of others that have used an existing filter but new substrate & have had major issues when adding fish shortly after setting up.

[Brennos]

I suspect the same thing also, Any recommendations as to how to keep this good bacteria, maybe replace substrate, and put old substrate in a filter bag or something? Or replace it and not worry, as I wont be increasing the bioload too dramatically.

[Jennifer]

Vacuum the substrate well and keep the water for the new tank. It will look mucky for a few hours until the filter does its job. However, if you know the filter is well cycled I personally wouldn't hesitate to swap out the substrate.

HTH