How do I increase alkalinity in my freshwater aquarium on the cheap?
I agree with kscottz that many tetras can handle a low pH. The only problem is that at about 5.5, your biological filtration will cease, and you’ll have ammonia start to build up. In turn, this isn’t much of a problem at a pH of 5.5, as most of the ammonia is of a non-toxic form at that point. Unfortunately, the first time you do a water change with water at a higher pH, the remaining ammonia in the water changes to a toxic form very quickly. Agitating the surface is good — either with the filter, or perhaps even with a small airstone. If the issue is CO2 build-up, this should raise the pH. If it doesn’t, you’re going to want to buffer up the alkalinity of your water. The simplest way, if your tetras are a species that can handle a pH of around 7.6 – 7.8 (a bit on the alkaline side) is to add a small bit of calcareous rock or gravel to the tank — like the “crushed coral” that used to be commonly used in marine tanks. In a freshwater tank, this will establish a fairly reliable slightl
No, kscottz is right, Tetras generally prefer low pH of ~ 6.5 (they’re a South American / Amazonian fish from waters full of tannic acid, etc). Having said that, aquarium trade ones seem to be pretty tolerant of anything you throw at them, although they won’t do really well in alkaline water. If the nitrogen cycle has run its course, then now’s the time to let the tank settle and find a good equilibrium. If you’re really worried about pH, try introducing some plants to help raise it by soaking up some of the CO2. I wouldn’t be overly concerned, unless you’re really wanting to keep things with exotic requirements (not likely in a small tank like that) – you’re best off letting it find its own status and choosing fish accordingly. Oh, and pH – like hardness – is due to and affected by a whole lot of environmental factors (e.g. Ca hardness affect/effects pH a lot more than Mg or other mineral hardness). Trying to keep pH, hardness, etc to particular levels purely by chemical addition is i
On preview posting: nonliteral is right about the effect of pH on biological filtering, and the addition of calciferous material to raise/buffer the pH. It’s just that personally I (a) wonder how much bio-filtering capacity there really is in such a small volume of substrate / filter (unless you’ve got a large external biofilter), and (b) the point of going too far overboard trying to maintain a situation the tank dynamics really don’t want to keep. Horses for courses though – one thing aquarium practices are guaranteed to do is cause “spirited discussions” (i.e. arguments 😉 amongst aquarists!
Just be sure that if you plant your tank, you remove decaying plant material right away, because that will lower the pH as organic acids leach into the water. It’s also going to be very important to have good lighting- plants need the light in order to use up the CO2 as they photosynthesize. My congo and bleeding heart tetras are really happy in their heavily planted tank.
