low ph and alkalinity in 20 gallon

[calla]

My tank is about five months old..

20 gallons
Tetra whisper filter 40
gravel substrate, real and silk plants
78 degrees
weekly 25 percent water changes, with conditioned water, and gravel vacuum
3 black skirt tetras, 2 white
1 common pleco


Everything has seemed to be fine with this tank, with the exception of my hard water... but when I recently tested the water I noticed the nitrates were a little high. Still safe, but around 30 ppm. I wanted to fix this, and my hard water (even though gh is not vital for their health...), so I started to do water changes 2 times a week, of 20%, using spring water from the store.

This worked, but created a new problem. These are todays results from testing the water..

Ammonia 0
Nitrate 15
Nitrite 0
GH 75
Alkalinity 20 !!!
pH 6.5 !!

... before all of this my pH stayed constant at 7, and alkalinity was around 80, what should I do to fix it? I don't want to use chemicals to raise the pH....

suppose I should have stuck with my hard tap water since that the only problem it had....

[Zerileous]

you could go back to the tap water if it was not causing any problems. You could also mix spring and tap water to have softer water but not too soft.

ps. just in case you didn't know this, your pleco will outgrow the tank so you should make arrangements for its future.

[calla]

I knew plecos could get big, but I didn't know they would become HUGE after that... haah... he was just a two inch baby when I got him a few months ago and is already about 5in!

but I plan to move him to my 55 gallon soon... that should hold him till I get the tank I've been wanting, a 100 gallon for my balas and pleco.

[Chrona]

Spring water comes from a spring. It's still got gH and kH (depending on the spring). Distilled water is pure water. You are just throwing more variables into the tank. Just use the tap water. It's what the fish are used to and fish are stressed by changes in gH far more than they are by a nonideal one.

[elmer]

Maybe you could use a mixture of distilled water and tap water - if you do, at least leave it out overnight to stabilize.