Questions

Hello I'm new to the saltwater world and I have 29 gallon bio-cube, I'm wanting to convert my 125 gallon freshwater tank into a fish only saltwater tank.  Looking for help on how to do that if anyone can help me that would be great.

 

I did this with my 55gal for reef. In my experiance it is almost cheaper to get a new predrilled tank plus it will look much nicer not having all that stuff hanging off the back of your tank. I do not what area you live in but if you have a good lfs near you they will help point you in a good direction.

Now since it is going to be fish only you wont need the lighting a reef needs which will save you lots. I would still suggest using live rock over artificial stuff, you just cant beat the flitration or the look. A good skimmer. I tend to lean towards one that is rated for 1.5x the size of tank im working with. And flow, you wont need as much as a reef tank but it will help your liverock and its biological filtration

Shop carefully, the cost can add up quickly but there are ways to keep that down by avoiding unneeded items and finding great deals from fellow reefers.

 

One more thing, IMO never take just one persons advice, and double check your facts. I found often times people have different ways of doing things, not everything works for everyone . I know some people that have gone with the very first suggestions they get and end up with problems. There is no reason to rush and there are plenty of people on this forum that are more then willing to help guide you.

 

Yes a tank with built in over flows is nice, but if you don't have one thats ok. you will want to remove you're old gravel or rock, and replace it with live sand or maybe go bair bottom, and live rock for your filtration and decoration. As said you will want a good skimmer.
Do some research as to the types of fish that you would like to keep as their requirements very from fish to fish.