Fishless cycle and number of fish advice

[jokerfac]

I have finished cycling using the fishless cycle method for the last month. The method recommends doing a 50% or greater water change because the nitrates will be high. However, my nitrates are zero due to plants. Should I still do a big water change before I add fish?

I am planning on having 5 zebra danios and 3 cory catfish in a 20 gallon tank. Is this too many fish? Obviously, I am not going to add all these fish at once. What would be the best order from your experiences?

 

[loganj]

I would do at least a 25% water change. Are you sure the tank has finished cycling? The fish load you listed will be fine. You could have a few more small fish without any trouble I think.

 

[jokerfac]

I am fairly sure it is cycled. The ammonia spiked off the test kit range. Then the nitrites spiked off the test kit range. The nitrates were high for a while, but then they dropped to 5ppm and 0 ppm while the nitrite remained off the chart. Finally, the nitrites have dropped to 0 ppm. Thanks for the advice.

 

[mound]

I'm sure you're fine.. I'd do a small water change just to make me feel better, but if everything is at zero, there's not really a need.

I fishlessly cycled a 125g tank recently - I waaay overdosed with NH3 up front (normal household kind, no perfumes/surfacants.. a 10% solution) I put 1.5 CUPS of it into the water at once.. holy sh*t that stunk, readings were WAY off the chart.. so I waited and waited.. after 6 days the Nitrites had spiked.. another 3 days later NH3 was at zero, N02 was going down.. 10th day my tank could completely convert to N03 approx. 6ppm of NH3 in 8 hours.. (yes overkill) Kept "feeding" it NH3 until my fish order arrived from Armkes.com.. approx. 30 small-medium sized cichlids. Did a 60% water change (Nitrates naturally were off the chart) which brought the Nitrates down to about 10, added the fish and they've been happy since, everything consistently reads at 0ppm.. ('cept N03 of course, no plants, so a 15% weekly change keeps that in check.)

(I should note, upfront I also added approx. 10lbs of lava/tufa from an established tank and ~1gallon of "filter mud" (I empited my Fluval 304 from the established 55g tank directly into the 125g tank).. I'm sure that helped..