Moving into a larger tank

[splatee]

Hello everyone,
I just took down our 240 gallon cichlid tank that i am going to use for our eels. I would like to use the Fluval 404 filters that were on there for extra bio filtering and water movement. In the current eel/fish tank we have roughly 60 - 70 lbs of live rock and about 50lbs of sand. In the 240 i had this rock called Texas Holley Rock about 150lbs or so that i would like to use with the live rock from the other tank. So here is what i will be running.
2 x Fluval 404
1 x CSS 125 skimmer
40 lbs of existing live sand with new sand
60-70lbs existing live rock
150lbs of Texas Holley Rock
Inhabitans:
2 x Zebra eels
1 x Chainlink eel
1 x Goldentail eel
1 x Dogface Puffer
1 x Lunare Wrasse
1 x Sailfin Tang
Now the 240 gallon is built in a wall, kinda like a room divider. Due to how tall the tank is, i was able to get out almost all the gravel but there is a little left and the rest of the water in the tank is pretty mucky, i can't get the rest out.
Is there any forseen problems with this setup? I plan on adding another CSS skimmer down the road. Can i use the existing filter media in the Fluvals just by rinsing it or should i boil it, since it was from a freshwater setup?
Thank you

 

[aw2x3]

Even adding another CSS Skimmer, that's not nearly enough filtration for that size tank.
I'd suggest nothing less than a skimmer rated for double the tank size, with that bio-load.
I'd also take the "Holley Rock" and let it sit in the sun for a few days, before just putting it into a salt tank.

 

[drewsta]

for that size tank I would do a 55-100G sump with a refugium. and 2 skimmers or a very large etss skimmer