I purchased a used Oceanic Biocube 29 from craigslist for $50. Met the buyer to pick it up and everything appeared to be in OK cosmetic condition. No scratched or cracked glass. Needed a good cleaning. Was told it was in use up to last week. He said the pump was ok but needed to have the cord jiggled every once in a while.

Initial Impressions and Problems:
Got it home and filled it with freshwater. Plug everything up and the pump was loud as could be. It makes a loud low pitched noise that oscillates about every 2 second. Remove the pump and find the that elbow had cracked so the previous owner decided to duck tape the elbow and return pump hose together. I have the pump in a 5 gallon bucket running outside. I'm thinking it might be due to buildup in the pump but if not I plan to replace it with a Rio 6HF. Regarding the broken elbow I will pick up some 1/2 PVC and will connect the pump directly to the wall without the elbow to fix this issue and increase flow.
I also noticed that the hood was remarkably quite. People mention mods about swapping out fans in the hood but I didn't understand why until I found the ultimate mod to make the hood quite. Lets just remove the fans completely and run it that way.

So now I need to add fans to the hood. I was think about picking up some Noctua 60x25mm fans unless something else is recommended. I see the pin connector on the hood is for a 2 pin so I ordered the following fans.
http://www.ebay.com/itm/400618743992
I'll remove the 2 pin cord from these and will splice them into the noctua fan. Anything wrong with doing this?
Cleaning:
I picked up some muriatic acid and would like to use it to completely clean the tank and possibly salvage the pump. I have seen people recommend a ratio of 1:10 muriatic acid and water at the same time I've seen 1:100 muriatic acid. What ratio should I use?
I have protective gear pretty well covered. Full body PVC suit , face shield, PVC gloves.
Any other recommend things to check if they are broken?
Planned Upgrades:
Noctua 60x25mm
Rio 6HF
http://www.ebay.com/itm/LOC-LINE-3-4-ROBO-ARM-Adjustable-Dual-Return-Nozzle-for-Aquariums-w-Flare-Ends-/281639499662?pt=LH_DefaultDomain_0&hash=item419305b78e

Initial Impressions and Problems:
Got it home and filled it with freshwater. Plug everything up and the pump was loud as could be. It makes a loud low pitched noise that oscillates about every 2 second. Remove the pump and find the that elbow had cracked so the previous owner decided to duck tape the elbow and return pump hose together. I have the pump in a 5 gallon bucket running outside. I'm thinking it might be due to buildup in the pump but if not I plan to replace it with a Rio 6HF. Regarding the broken elbow I will pick up some 1/2 PVC and will connect the pump directly to the wall without the elbow to fix this issue and increase flow.
I also noticed that the hood was remarkably quite. People mention mods about swapping out fans in the hood but I didn't understand why until I found the ultimate mod to make the hood quite. Lets just remove the fans completely and run it that way.

So now I need to add fans to the hood. I was think about picking up some Noctua 60x25mm fans unless something else is recommended. I see the pin connector on the hood is for a 2 pin so I ordered the following fans.
http://www.ebay.com/itm/400618743992
I'll remove the 2 pin cord from these and will splice them into the noctua fan. Anything wrong with doing this?
Cleaning:
I picked up some muriatic acid and would like to use it to completely clean the tank and possibly salvage the pump. I have seen people recommend a ratio of 1:10 muriatic acid and water at the same time I've seen 1:100 muriatic acid. What ratio should I use?
I have protective gear pretty well covered. Full body PVC suit , face shield, PVC gloves.
Any other recommend things to check if they are broken?
Planned Upgrades:
Noctua 60x25mm
Rio 6HF
http://www.ebay.com/itm/LOC-LINE-3-4-ROBO-ARM-Adjustable-Dual-Return-Nozzle-for-Aquariums-w-Flare-Ends-/281639499662?pt=LH_DefaultDomain_0&hash=item419305b78e