Why am I having a bacteria bloom 6 months after my tank has been set up?

Question

I rinse the filter cartridge in old tank water and do 20% water changes weekly. I don't think I did anything to mess with the biological filter. I have not added any new fish for months.

Ammonia 0
Nitrites 0
Nitrates 5

Answer 1

i would cut down on rinsing the filter cartridge, i rinse the filter cartridge every other water change, not every water change, sometimes this stuff just happens, i would go ahead and continue what your doing, dont start doing excessive water changes, as this messes with the bio also, i would stick to your 20 percent a week and just have patience, monitor all your levels and wait it out, sometimes it takes a few days, other last 4 weeks or more, patience is key, but excessive water changes will just prolong it, ive had this happen before if i got carried away with the gravel vac,

Answer 2

I assume the bloom is taking the form of cloudy water? It's sort of unusual for a bloom to happen at this late date,and you seem to be doing everything right. The water quality numbers you report bear this out. It might help to rinse the filter cartridge only on alternate water changes to allow the bacteria colony to grow a bit. Adding a very porous piece of rock or sintered glass ornament to a well aerated area might also allow for an increase in the beneficial bacteria. The solution to the problem is time to allow the water clouding bacteria to deplete their food source or be out-competed by the existing colonies. Sorry, but I don't think there is a quick fix. However you may take some small amount of comfort in the fact that you have those excellent numbers,your fish are not being harmed,and given time the problem will fix itself. Keep up the good work and good luck.

P.S. Doing extra water changes may actually prolong the problem. Stick with your routine. Although it's counter-intuitive the solution is more bacteria, not less. Hope this helps.

Answer 3

Sometimes a change in you tap water chemisty can cause a bloom of bacteria or diatoms in the tank.



Extra nutrients come in with the fresh water and feed the free floating critters. Harmless, but very annoying when you have the tank running well otherwise and are doing things right.



Because your nitrate reading is low you could probably skip a couple of water changes and see if it clears up. If it does, then do a water changes and see if it comes back. That will at least tell you if it's the tap water causing the issue. You may need to find a different water source or do more frequent smaller water changes?



Ian

Answer 4

sometimes, this can just happen, for the time being,do 25% water changes every other day until the problem is fixed. You may not have done anything wrong.

hope this helps!

Tobias