What is included with the 55 gallon tank for $150?
Depending on whats included, it might be better to start from scratch.
There are three routes you can take:
1. Reef tank - most complicated and most expensive.
2. Fish Only With Live Rock - Not as complicated but still expensive.
You can find alot of info here about live rock, the most common is Fiji Live rock. The cheapest I have seen at local stores is $4/lb, in a 55 gallon, anywhere from 60-90 lbs would be sufficient. Buying from a local store decreases your cycle time due to less die off because of decreased transit time. You tank will cycle pretty quickly and will have alot of beneficial life with the introduction of live rock.
3. Fish Only With Dry Rock - Same as 2 but cheaper. Does not have any nice looking coraline aglae. Takes longer to cycle, i.e. will take atleast 6 weeks before you can add your first fish or two. Dry rock could be any calcerous limestone rock. This is commonly called baserock and sells for about $1-2/lb. Mixing this with live rock can spread the pretty algae and decrease cycle time.
With any of these 3 routes you will want aragonite substrate on the bottom. 1-2mm if a good grain size. Its small enough to not trap fish waste and food but large enough not to cloud your tank and can also be vacuumed. Aragonite will help maintain the pH and water chemistry along with the rocks.
With route 2 and 3, you wont need as much water flow as a reef tank. Get two powerheads rated around 250 gallons per hour or two aquaclear 500's and you should be fine.
Live rock will need a bit more lighting so look in to power compact lighting with a glass hood. Dry rock wont need as much lighting, so a stock hood would work fine. If you want to do a mix of live rock and dry rock get power compact with the glass hood.
Get two reliable heaters, Visitherm is good. Make sure the temperature never fluctuates more than 2 degrees. Temp should remain around 78-80.
Fill the tank up with RO
filtered water. The stuff you get at Target or Walmart in the gallon jugs. I wouldnt use tap water.
You will need a test kit for ammonia, nitrite, nitrate and pH. You can only add fish after the tank is cycled and ammonia and nitrate are zero, pH should be around 8 - 8.3. Your salt mix should take care of that.
I cycled my tank with hermit crabs and shrimp and snails and decaying food. Once Ammonia and nitrite hit zero I bought a fish, and added one or two every few weeks after that.
Did I miss anything?