Bulk Reef supply Two Part

[turtleone]

I recently did some housekeeping on my 25 gallon tank,witch included scraping all the coraline algea from the glass in front. My quistion is after doing so I get a white film (hard) needs to scraped of glass with A scraper. I use Bulk Reef supply two part calcium and alk solution. when I add the alk supplement is when film appears the very next day. I no its the alk solution because if I add there recipie two for alk witch includes baking soda it does not happen. My calcium leval is at 420 and alk is at 10DKH I have to add 30 ml of each per day to keep at this level. Is it the coraline algea trying to re form or come back. Please forgive spelling.

[HighlandReefer]

Sounds like it is likely a calcium carbonate film produced from having a higher alk level and perhaps from a high localized pH level caused by using high pH alk supplements. If you are dosing the alk supplement near the glass, perhaps dosing it in a sump will help. I would drop your alk level down to around 9 dKH at least. Many alk kits are off and perhaps your true alk level is higher than you think, perhaps over 11 dKH which above this is much more conducive to calcium carbonate films and deposits on equipment.

Alternatively using regular baking soda will reduce this since it does not create high pH localized areas in your tank water when added. ;)

[bertoni]

I agree that the film sounds more like a precipitation problem rather than coralline. You could try dosing baking soda instead of the two-part for a few days, to see whether it causes precipitation. Baking soda is a low-pH additive, so it's less likely to cause problems.