Originally Posted by Chris7 (Post 1348186) I did something kind of close,I had a cycled 10 gallon gravel tank. and Bought a 35 gallon tank and transferred everything filter materiel included into the 35 with no fish to start. But had only a part bag of old play sand left over.So I used the gravel from the 10 gallon first and then added the sand on top. Tank as been running for 7 weeks and everything as been good:-D! PS: is that a Scout in your profile Pic??? Cool truck!!

Originally Posted by Boredomb (Post 1348214) Unless you put enough sand in to completely cover the gravel and account for it settling in between the gravel. The sand will just settled in between and the gravel and the gravel will still show up. This might take awhile but eventually it will happen. Posted via Mobile Device

Possibly, yes, as you would be suddenly suffocating the existing substrate. It is never good to mix different substrates, thinking here of different sizes, as Boredomb mentioned; they will mix with the gravel on top.

The substrate is the most obvious part of the aquascape if it is "different" in some way, and as it is also the most complicated to replace it is best to decide what you want and do it at the start. I have changed my tank substrates over many times over the years, and during the past 2 years five of seven tanks were torn down and changed. It is the easiest way to do it.

Byron.

Originally Posted by marshallsea (Post 1348288) Do you think the sand covering the existing muck underneath the gravel would cause a problem?