Help! Nitrates above 160ppm after water change and killing fish!

[Dystinction]

I agree with some of the above recommendations. It will be some additional cost investment, however an RO/DI unit will pay itself forward immensely in the long run.
Personally, I don't like to put the 'care' of my water in anyone else's hands. The RO/DI will provide you the platform to both have your own top-off water, and supply for mixing your own salt.

 

[Dom]

Don’t know if this matters but I used API Quick Start and my Nitrate cycle completed before adding fish. I also added them gradually

I'm sorry, but 6 fish in 6 weeks is NOT gradual.

I have a build that is 8 months old and still only has 1 fish.

 

[Armani Garcia]

You can see the algae buildup on the glass after me cleaning it just yesterday

 

[Crabs McJones]

I agree with some of the above recommendations. It will be some additional cost investment, however an RO/DI unit will pay itself forward immensely in the long run.
Personally, I don't like to put the 'care' of my water in anyone else's hands. The RO/DI will provide you the platform to both have your own top-off water, and supply for mixing your own salt.

Thats another good point! Thanks for bringing it up. what are you using for your top off water to keep the tank full between water changes?

 

[Flippers4pups]

What

You can see the algae buildup on the glass after me cleaning it just yesterday

You tank is nowhere capable of handling all that bio load.

 

[Crabs McJones]

You can see the algae buildup on the glass after me cleaning it just yesterday

I can immediately see why your nitrates are so high. You have a huge bioload with your fish selection, and two pieces of live rock that are NOT able to filter out your water even with the hang on back filter.

 

[Armani Garcia]

What do you consider gradually given that the tank is a month old?

1-2 fish every two weeks or so

 

[Dom]

Is the live rock in the picture the only live rock you have? Do you run a sump with live rock in it?

 

[Flippers4pups]

Okay, slow down and please read this:

https://www.reef2reef.com/threads/the-supreme-guide-to-setting-up-a-saltwater-reef-aquarium.138750/

You need much more rock in that tank to handle nitrification.

 

[Crabs McJones]

Is the live rock in the picture the only live rock you have? Do you run a sump with live rock in it?

Based off the picture, I see an intake for a hang on back filter, i'm guessing no sump.

 

[Dom]

1-2 fish every two weeks or so

I usually go months between adding a fish.

Understand this: Every time you add a fish, you will see your ammonia rise because the nitrifying bacteria colony needs to grow in order to handle the additional bio load of the new fish.

I'm guessing ammonia is he real culprit here.

 

[Armani Garcia]

Based off the picture, I see an intake for a hang on back filter, i'm guessing no sump.

Yes no sump

 

[Fin]

Whoa Nellie! Slow down.

 

[Dom]

Based off the picture, I see an intake for a hang on back filter, i'm guessing no sump.

I looked for that; didn't notice it at first. Now I do.

 

[Armani Garcia]

Thats another good point! Thanks for bringing it up. what are you using for your top off water to keep the tank full between water changes?

Conditioned Tap

 

[Flippers4pups]

Conditioned Tap

Let's take this one step at a time.

What's your current water pramameters?

 

[Dom]

Was this a fresh water tank that you converted to salt water?

 

[Armani Garcia]

Was this a fresh water tank that you converted to salt water?

No

 

[Armani Garcia]

Let's take this one step at a time.

What's your current water pramameters?

High Ranged pH: 8.0
Ammonia 0.25
Nitrite: 0ppm
Nitrate: 160ppm

 

[Crabs McJones]

At this point, my best advice would be:
1. Purchase an RO/DI unit and salt mix to make your own pure water at home, NO MORE tap water whatsoever. Tap water contains all kinds of junk (ammonia, nitrites, nitrates, heavy metals, chlorine, chloramines, dirt, and other chemcials that your city might add to the water supply) that even for fish is no good.
2. Surrender your fish to your local fish store before the rest die
3. Setup your 125 (since you were going to do it anyway) and do a tremendous amount of reading, there are alot of good threads on here to help you out, of which I can link to you if you'd like.