Oilly film and PH help please!!

[Andy189]

Hi everyone. I have been feeding my arowanas and stingrays for the past few weeks with chopped smelt, salmon and shrimp. I haven’t pay much attention at the surface before but I noticed the oil film on top after doing waterchange yesterday. It was very thick film. I have 2 wave maker and the return pump make the surface moving like crazy but still have that oil film. Is there anything I could do to break that?
Also I checked my water and the PH dropped to 6.0 from 7.0. My water before was stable at 7.0 for the last 2 years until I started to feed heavy on shrimp and salmon last 2 weeks to pump up the stingray pups. I have roughly about 15lbs of crushed corals in my sump. Should I add an other 10lbs to increase the PH?
Any input with help a lots. Please give me some advice. Thanks everyone

 

[Rocksor]

Start to skim the top of the waterline every day with a container or look into a DIY protein skimmer like duanes has made for freshwater. Breaking water surface tension is not removing it since oil will not mix with water. What you are feeding is contributing to this.

Increasing nitrogenous breakdown (from what you are feeding) of organic compounds is eroding your KH, and causing the PH to drop. Get an API liquid test kit and see what the KH is of your source water (tap water). If it is only 4 degrees or lower, then your tap naturally is borderline in allowing PH to drop.

Increasing water changes (frequency and volume) will help with both oily film and KH dropping.

 

[Andy189]

Start to skim the top of the waterline every day with a container or look into a DIY protein skimmer like duanes has made for freshwater. Breaking water surface tension is not removing it since oil will not mix with water. What you are feeding is contributing to this.

Increasing nitrogenous breakdown (from what you are feeding) of organic compounds is eroding your KH, and causing the PH to drop. Get an API liquid test kit and see what the KH is of your source water (tap water). If it is only 4 degrees or lower, then your tap naturally is borderline in allowing PH to drop.

Increasing water changes (frequency and volume) will help with both oily film and KH dropping.

Im doing about 2 waterchange a week with roughly around 40-50% each time. Is there any other way to get the ph back to stable 7?

 

[Rocksor]

Im doing about 2 waterchange a week with roughly around 40-50% each time. Is there any other way to get the ph back to stable 7?

You need to measure the KH of the tank and your source water. This will allow you to determine precise measurements to get your KH high enough that the PH doesn't go down over the course of the week.

In the meantime cut back on the heavy feeding to 1/4 until you can get the KH test.

 

[Joshuakahan]

Hi everyone. I have been feeding my arowanas and stingrays for the past few weeks with chopped smelt, salmon and shrimp. I haven’t pay much attention at the surface before but I noticed the oil film on top after doing waterchange yesterday. It was very thick film. I have 2 wave maker and the return pump make the surface moving like crazy but still have that oil film. Is there anything I could do to break that?
Also I checked my water and the PH dropped to 6.0 from 7.0. My water before was stable at 7.0 for the last 2 years until I started to feed heavy on shrimp and salmon last 2 weeks to pump up the stingray pups. I have roughly about 15lbs of crushed corals in my sump. Should I add an other 10lbs to increase the PH?
Any input with help a lots. Please give me some advice. Thanks everyone

I would also stop with the salmon, something like fresh tilapia is much less oily

 

[duanes]

If you must continue using oily fish, getting a protein skimmer (fractionation unit) strong enough to work in fresh water may be needed.
Below a video of a DIY one I built for a small koi pond, you can see the waste billowing out, these units also reduce nitrate by removing nitrate precursors.
I have also used them on inside tanks in the fish room.
koi pond fractionation