Aquarium water too acidic

Question
Hello Nicole,

I have read some of your articles and I hope you can help me.  My aquarium water is too acidic. A few weeks ago, whilst on holiday, a friend of mine feed my fish for 2 weeks and used 2 whole jars of flake food in that time.  The fish were greatly over fed and eventually died.  When I introduced new fish in the tank they died within a couple of hours.  I did a water test and my water was far too acidic.  The ammonia was over the roof too! I have done several water changes since (about 50% once a week) and this has reduced the ammonia to normal and brought the acidity down but not completely eliminated it.  The PH is now about 5.5 but I think it needs to be about 7.  I usually keep freshwater tropicals and intend to continue.  I have a lot of plants in my tank, so I don't really want to add chemicals unnecessarily if they will hurt my plants.  Is there something I should be doing which will reduce and control my PH more naturally?  Thanks for your help Nicole.

Answer
Hi Raj,

I'm certainly familiar with this story! I've also come home, horrified to find the entire substrate covered in a rotting flake mess and found that three month's supply of fish food was gone in a week - thankfully, my fish managed to recover, but just barely. Now, when I go away, I leave Ziploc bags full of pre-measured food in the refrigerator for the sitter and hide all of the other fish food!

I believe what you need to do, apart from the water changes, is run some kind of media in your filter that absorbs organics from the water. I have a small internal filter that I use expressly for this purpose. Use something like Boyd Enterprise's Chemi-Pure (a granulated carbon with resin beads) or Seachem's Purigen (resin only) and see if that helps. If you can't find these brands, see if you can find an equivalent. Even plain activated carbon will help, although it won't last as long...you will probably have to replace it in a week.

To buffer your water back up, I suggest you use what they call "Malawi salt mix" - it is a safe and natural way to add carbonate hardness back to the water. You can mix some up yourself, which is far more economical, or you can buy some already made. Seachem sells some:
http://www.seachem.com/products/product_pages/MalawiBuffer.html

Here is a recipe to make your own. Per 5 gallons:
* 1 teaspoon baking soda (sodium bicarbonate)
* 1 tablespoon Epsom salt (magnesium sulfate)
* 1 teaspoon marine salt mix (sodium chloride + trace elements)

If you ever need to convert to metric, this site has everything:
http://www.convert-me.com/en/

Please do let me know how this works out for you. Keep up those water changes! Also, for now, try feeding the fish mostly vegetable based or "green" foods such as Spirulina flake. The lower the protein content, the better, since high fiber, low protein foods are not going to pollute your water as much. Naturally, you ought to cut back on the feeding until your tank stabilizes again - the fish will be just fine with one light feeding daily for as long as necessary.

I hope that helps! Take care.
Nicole