Very slow cycle, 550 US Gallons tank

[Jamal Haidar]

Hi, I am facing difficulty cycling my new 550 gallons tank. I started tank cycling with one 16'' spotted gar but after 6 weeks Ammonia still high in the range of 1-2 ppm and not showing signs of falling down. I perform regular water changes to prevent Ammonia from exceeding 2 ppm. I own other fresh & salt water tanks and all were cycled within 6 weeks.

The tank dimensions is 3X1X0.8 m fiberglass with the Tetra pond Bio-Active pressure filter BP4000-UV rated for 4000 gallons (an over kill). The pump is tetra DHP4200 with flow rate of 4235 GPH. Water tempreture is 26° C and PH is 7.5.

I conduct testing regularly with API and JBL test kits however results are contradicting. After 6 weeks, Ammonia reading 1-2 ppm with API Kit, while its 0 with JBL kit. Nitrite is 0 with API and around 0.1 ppm with JBL and never increased beyond that in 6 weeks. Nitrate is not detectable yet with both kits.

I don't know what seems to be the problem? Why Ammonia is still high after 6 weeks. is it the filter that is slow in growing sufficient population of bacteria? Do anyone have an experience with Tetra pond pressure filter. Is it possible that the cycle is complete but the test kits are not accurate? Or is it normal for the cycle to take more than 6 weeks in some cases? What shall I do to complete the cycle faster? Any advice please.

Thanks and sorry for the long post

 

[xraycer]

I believe that your your tank is nearing its completion in cycling. Yes, it takes a little more than 6 weeks to build up the proper bb population when starting from new materials/supplies. All you can do at this point is do frequent water changes to prevent ammonia and nitrite from accumulating too much. By frequent w/c, I mean every day or 2, at 30%+

 

[Jamal Haidar]

I do 30% WC twice a week currently. I will try to increase it if I can and keep an eye on ammonia and nitrites.
Thanks for the advise

 

[Jamal Haidar]

Finally tank cycle completed after nearly 10 weeks.



Ammonia not detectable, nitrite not detectable and nitrate at 10 ppm.

Time to move my RTC

 

[kno4te]

Alright now for some fish and updated pics.