My cories and new tank

[malignau]

Hey guys,

I have a 25L tank with 5 bronze cories atm (lol yes i know its overstocked). The tank is really well planted, has sand substrate and and my cories seem very very happy. They've gained so much colour and have become so much more active in the last 2 months since i brought them home. They have also bred at least on 20+ occasions in the last month. I have a breeding net full of the fry atm.

The thing is, after numerous delays in getting access to the 44 gallon tank (due do parents being indecisive) i have now finally set up the tank filtering. Im going to be moving my cories into the 44 gallon tank and im trying to decide whether i should stick with sand substrate or go with black gravel. Fish poo shows up so much easier in white sand and will also make my tank hard to plant, what do you guys suggest? I want my cories to be as happy or even more happy with the new tank, but i want to keep the tank relatively easy to maintain so i dont need to be cleaning the substrate every few days.

Also since i wont be able to use an undergravel filter with sand, should i upgrade my canister filter which only pumps 300l/h atm (old filter my dad used to use years ago) or supplement it with a hang on filter (was thinking aquaclear as this is what i have on my current cory tank).

Another thing is my cory fry are still quite small.. ranging from 1 week old to 4-5 weeks old, at what age would it be safe to move them into a new tank? i dont want them to die on me =[

Thanks for your help everyone =]