ph raising

[Airli]

the ph in my tank keeps rising. its only a small 9 gallon tank and other parameters are fine. it is not overstocked but has only been going for 2 1/2 months. my tap water is quite alkaline i cant remember exactly but in the mid 8 range i think. i use ph down and keep my tank at 6.6 6.8 and when i test the water about 4 days atfer a ater change it is the same. but by the seventh or eigth day when i do my water change (1/3) it has risen to be quite akaline, cant remember exactly. My tank does have brown algae on my fake plants and gravel(actually i think its diatoms?) which has been there for a couple of weeks. could this be altering my ph? i thought that this brown stuff wasnt harmful...

any thoughts?

 

[Paul_MTS]

what are you keeping in the tank?

if they don't specically need those parameters then don't bother changing your PH.

the fish will prefer a steady high PH rather than a up and down PH.

 

[Airli]

at the minute it only has 4 zebra danios and a corey.

 

[Paul_MTS]

i'd leave it alone then.

 

[Airli]

ok so i tested my tap water an its like 8.5

i am cycling a 34 gallon at the moment and am planning on putting in
angels (like 6.5 - 6.9)
bristlenose cat (likes 6.5 - 7.4)
cory (6.5 - 7.5)
harlequin rasboras (6.8 - 8)
pristella tetra (6-8)

i know these are only guides and the fish can be fine outside that r ange but i still think 8.5 is to high..

does anbody have their tank at this kind of ph?

 

[pica_nuttalli]

the chemical effects of "pH Down" are simply wearing off as time goes by. the easiest and best way to lower a tanks pH is through the tank decor. see if you can't incorporate a significant amount of driftwood into the tank. make certain you don't have alkaline substrate material, decorative rocks, shells, etc. which will leach into the tank water and work against your other efforts. peat in the filter is also a typical natural method of lowering pH; not precisely sure how it works but i bet someone could say.