Do have a think about sticking more live plants in. None of the plants but one (wisteria) in my 3.5 are actually in the substrate - the java fern's on wood and the anubias & crypts are potted . All the others float or sit on the substrate - and the tank's pretty much stuffed so that if the water chemistry goes haywire in the night, there's at least plants in there to sink some of the toxins. I find the tank vastly more stable planted than not, also - a LOT less mini-cycles happening (I've had one in the past several months, caught it early and dealt with it, none since).
I agree with Freya's post above - but really, it'd help to test your water daily until you see ammonia. Change water, repeat. This would give you a ballpark idea of how often your regular changes need to be. Every tank is different..
If you're cashed up, you can get stick on ammonia and nitrite alerts. I really want some for the small tanks, but at 36 bucks each at my Very Expensive LFS, it's a luxury..
And yes -- a 3.5 CAN cycle, mine is well and truly cycled. Thing is, with small tanks there's way less room for error and malfunction, and the cycle can very easily be thrown out of wack leading to potentially dangerous mini-cycles. Yet, despite all the emphatic nay-saying I've heard, it IS possible to keep a 3.5 cycled and stable. It requires a bit more vigilance, I think - but hey, large tanks crash too and kill fish too. It's a matter of getting to know your tank and fish so any warning signs can be observed (Cleo tail-clamps at .01 ammonia, lol.. I always know when something's up just by looking at her..) and regular testing to keep parameters in order.
Last edited by Aus; 08-02-2012 at 10:39 AM.