water change with tap water

IMO you're asking for trouble if you use tap water to do any water change. Just my 2 cents.

 

It could also be that the RO machine needs new filters/ membrane. I would try testing the RO water prior to adding to your tank and see if it still gives you the same reading.

 

OK lets look at possibilities to try to establish solutions.

Bad test kit--solution, buy another test kit, salifert kits are really popular. Perhaps you can get a refund for the kit you have now if it is bad.

Shooting from the hip on this one, not familiar with the api kits but what is the max nitrate level it will detect? is it possible that 100 is the highest and your nitrates were over this?

Bad RODI water--solution check rodi water before mixing and doing water change, if nitrates/high TDS are present tell the LFS to change their filters. Or even better invest in your own RODI.

Another possibility is operator error when performing the API test--solution read the instructions and make sure you fully understand them then follow them precisely. Again not saying this is the case, just a possibility.

And in no way would I use tap water to mix new salt water with or even for topping off.

 

I just tested the RO water I use for my water changes and it has 0 nitrates in it. I also tested my tank water again and it shows about 100 (maybe more as the color difference between 80 and 160 is only slightly different), max the test goes to is 160.

I need to look into ways of reducing my nitrates other than water changes. I was actually thinking I might have some die off on my live rock as there are a what looks like a few dead white worms on some pieces.

 

Only way your nitrates are going to come down is water change. Do you have a LFS that sells salt water or, at least, RO/DI water?

 

Year the heck out of the tap water before you use it. How good your tap is changes city to city, so unless you are talking to a local on here it is impossible to say. I personally use tap water and its always been fine, but we have really good an pure tap here. In the very Lear you will want to add a dechlorination solution to it.
Avoid the machines at stores at all cost. 75% of the time your tap will be better than the water from a store machine. The reason being is most store machines are terribly neglected and don't have the filter changed nearly as often as they should, and you end up with water with even higher concentrations of TDS than the tap its suppoaed to be filterng. Test the heck out of it before using to make sure.

 

My LFS sell the RO/DI water for 20 cents a gallon which is where I have been getting the water for my water changes, but I only have enough containers for 18g at a time and I save 3g for top off water. My LFS has told me 15g every 2 weeks should be fine the only think I can think of is I have been greatly overfeeding my fish (twice a day) and have not been testing my water often enough. The lady i got the tank from used tap water only for about 2 years and had a huge lion fish and moray eel, I'm not willing to take the chance with tap water unless I have no choice.

Its been an expensive mistake not testing my water often enough and having no quarantine tank. No more fish will be added until my nitrates are under control and I have a quarantine tank.

Thanks for everyone's help.

 

What type of filtration system do you have for the tank? Sump? Skimmer?