Calling All Chemistry Majors

[plantropimunity]

Hi there. i am currently setting up what will be a freshwater planted community tank.
it is a thirty gallon tank, and the planned inhabitants are as follows.
zebra danios
black neon tetras
lyretail killifish
german blue rams
freshwater clams
amano shrimp
wisteria
java fern
melon sword
using drs. foster and smith as my guide i have arrived at the following goals for this tank's chemistry
ph:6.6
kh:7
temp:74f
and obviously
nitrate, nitrite, ammonia: 0
phosphate: 0
i dont know if the phosphate really needs to be that low, so i guess that is part one of my question.
part two is this: how can i maintain a kh of 7 while keeping ph on the acidic side?
i am switching from a ten gallon to the thirty, and when i tested these today kh was 0-1 and ph was 6.0.
that tank has only the danios and the tetras in it, and they seem okay, but the tetras could be more active i think.
any suggestions are welcome. thanks

 

[jayjay]

how are you planning on keepin the nitrates so low, your tap water probably has nitrate of about 20ppm, if you were planning on keeping it that low you would need alot of plants just a few fish and to change the water alot more often. sorry lol just pointing that out.

i have only ever kept freshwater clams ina pond but i duno if they are still in there and i don't no anything about them.

sorry i can't really answer any of your questions but that pH would be good for the fish you've chosen i think. and what do you mean i thinnk the tetra's could more active? has your tank cycled if it's not then you'll need to sort that out if it's not read the pinned links in the forum on cycling.

 

[Kairi]

i don't think a reading of 0 for nitrates is possible w/o a heavily planted tank. nitrates up to 20 aren't bad for your fish... so having some won't hurt anyone.

 

[dylema]

To maintain a pH you need to have the right buffer. A buffer is a solution with particular amounts of acid and base. If you want to have a particular level of base you need to work out how much acid needs to be added to get to your required pH. When I say add acid I don't necessarily mean actually adding acid (like vinegar)it could be the conjugate acid of the base you are using.

Since your pH is lower than you want and so is your kh I would think you need to bring up the level of kh and see what your pH becomes. It might work out to be good without messing around. I would speak to a good LFS to get the right stuff to add for your kh and then work out if you need any more buffering up or down to get the pH right.

Wow I don't think I could have made that more confusing. Hope it helped a bit.

Edit: Since you are having a planted tank the pH buffering could be controlled by addition of a kh increasing product and the addition of CO2. (CO2 makes carbonic acid) however looking at a chart I just found that would mean a CO2 concentration of about 50ppm at a pH of 6.8 it would need about 30ppm CO2.

 

[plantropimunity]

thanks to all who replied.
i listed my desired nitrate level at zero because that is what i am going to shoot for. my tap water tests at zero nitrate, so that is what i start with, and what i will try to keep.
dylema, your reply wasnt really as confusing as you may think. i do have experience keeping fish, so i understand the concept of buffering, its just that when i add buffer to the water for my cichlid tank, it automatically kicks the ph up. since i want the ph to be a little on the acidic side, how can i buffer the water properly (get the kh to 7)?
anyone else have any ideas?
i was thinking of playing around with baking soda tomorrow and seeing what amounts take the ph/kh on what rides.

 

[k.o.d]

This isnt about the application of chemistry, it is about providing stable conditions for your fish

If you constantly play with chemicals to try and balance your system to the optimum you will as a by-product stress your fish from the changes you make, fish will tolerate higher or lower pH levels than their norm but will not do so well if it constantly changes, your tank will become more acidic between water changes dependent on the buffering capacity of your tap water

pH is a logarithmic scale so changing the pH by even 0.5 changes the H+ ions by a large amount.

Nitrates are a natural by-product of respiration and excretion, smaller fish will pollute volumes less than big messy eaters but although admirable you may well have to accept certain levels of nitrates

I am happy if my nitrates are below 80 in my ray tanks

Steve

 

[dylema]

OK I agree with k.o.d. but if you find an appropriate buffer this will help maintain a stable pH. That is what a buffer does, it resists changes in pH. So you will not be changing the pH day to day. with no buffering capabilities when you do a water change, when fish poo, if you add CO2 your pH will swing quickly. If well buffered these things will change the pH far less than if the water has no buffering capabilities.

 

[plantropimunity]

its worth mentioning here that i am talking about a tank that right now has nothing but water, a heater, a thermometer, and a filter.
the idea is to prepare the water before i put anything in it, so that when i get the fish and things in there, i have already figured out my maintenance needs.
what if anything do you guys do to prevent ph swings?
k.o.d., i am trying to determine how to provide the most chemically stable conditions for my fish, so i think that since i am dealing with different concentrations of ions and levels of buffer i am in fact trying to control the chemistry of the water in my tank. that said, i appreciate your response.