High Alkalinity

Question
My tap water has very high aklinity and pH.   The pH is around and the akalinity (KH)is around 200 ppm. Its a small tank filtered (Undergravel), lighted but unheated 2 gal with two little zebra danios.  The fish were added 3 days ago.   The tank water has pH is 8+ and the akalinity (KH)is 300 ppm.   Is this part of cycling?  Should I try to lower the pH or alkalinity on the water change?  Should I use different water (store bought?)

Also, my house gets cold at night.  The tank is heated by the light to 72F but drops to 68 at night.  Will this be a problem?

Answer
Hi TH, first of all I must say I am sorry I haven't replied sooner. My computer has been not working well for the past couple of days and it wouldn't even allow me to send my reply letter back to you no matter what I tried!

Your high pH and alkalinity shouldn't too much of a problem to your zebra danios. Zebras are a tough species. They would prefer a lower pH but I don't reccommend trying to adjust your pH with chemicals and additives--why? Well, simply because attempting to adjust the pH with a acidic compound will do nothing to help. It will lower the pH for a while but by the time you test again, it will be right back up again. This is because of your high alkalinity which buffers your pH and without doing something about the high Alkalininty of your water, your pH will always go back to what it was no matter what you try. To soften water you need to remove minerals and calcium from it. Filtering your water through peat moss is an excellent way to lower your pH and hardness. This is because peat releases tannins and binds calcium--releasing acid. And if changed regularly, peat moss makes a reasonable solution to softening your water. But there is still problems...
Whenever you add fresh water--you must doctor the new water to match the original! This is quite a lot of work and trouble, but it is fortunately not neccessary for most tropical fish. The fact that you must remember is captive fish are very adaptable and nearly all but the most delicate do fine in even out of their preferred water chemistry range. Some even soft water fish have been bred in hard water in some instances. The important thing to remember is fish thrive in a stable not SPECIFIC chemistry. So quite simply, a stable but not ideal pH range is much better for the fish than an adjusted chemistry which has the potential to flucuate with the constant addition of chemicals trying to make it a specific pH. The main question you should ask yourself is how are the little zebra danios doing? Are they lively, brightly colored and eating well? If so, their water is fine. Nearly all aquarium fish do much better and need nothing more done to their water than frequent water changes.

I am afraid a temperature drop from 72-68 F would be stressful for your danios. An aquarium shouldn't really drop more than a few degrees over several hours. It is best at a constant range with very minor flucuations. My best advice is to simply leave the aquarium light switched on in the aquarium to keep in warm throughout the night. You should give your fish a source of shade from the bright light by provided tall and bushy plants--live or plastic... A ten times better option is to get your little danios a 10 gallon aquarium so it can be heated by a good aquarium heater and where the water quality would be more stable. If this is a little too much you might try to move your aquarium to a warmer spot in the house. Zebra danios don't have to be in any special water temperature but it should just be stable like the pH. And it should be warm.

My best wishes to you, I don't reckon the cycling process would affect the pH. More likely it is simply your tap water chemistry. Always be sure to test for ammonia every day in your aquarium and if it should ever be out of the safe zone, do a 30%-50% water change immediately. Always make the replacement water the same temperature as the main aquarium and is properly dechlorinated.

~Happy holidays and Happy fishkeeping!~
Karen~