RSS Facebook Twitter YouTube




Nitrite/overstock/HMF-filter pump capacity?

Home Forums My Aquarium Nitrite/overstock/HMF-filter pump capacity?

Viewing 2 posts - 1 through 2 (of 2 total)
  • Author
  • #303150



    So it’s been 2 months since our indoor pond was upgraded and HMF-filter was installed. Here is the thread for HMF-filter advice i posted with pictures of the old/new set-up.

    The filter size is 5cm thick with fine pores, 170x30cm with two pumps, one 1000L/h and 1200L/h. Both have 10-20cm tubing with 90degree bend connected (not shown in the pictures in old thread). I have ordered a 5cm 20ppi mat but it’s not arrived, so for now we have the fine mat installed.

    So apparently the tank is overstocked, and the flow over the mat-filter is too slow because I get nitrite (NO2) readings in the pond, which only started in the last two weeks or so.The filter was inoculated with bio-gel of some sort.

    13 fishes are in the pond. 2 goldfishes with “feathery pretty tails”, 1 normal goldfish, 4 koi, 3 common plecos, 1 featherfin, 1 Chinese algae eater, and 1 bristle-nose. 

    Both the feathery goldfishes are pretty big (>20cm) and very old with lots of tumor looking bumps (it still eats well, swim and look normal, but ugly), 3 of 4 koi are relatively large (up to 20 cm) and all 3 plecos are large, with the largest about 22cm, only the bristle-nose and one koi are pretty small. We don’t know the age of any other than the kois and the normal goldfish, but i’ve worked here 4 years, and they were still big 4 years ago. Some might be up to 10 years, but nobody knows.The goldfish appeared out of the blue as a fry last fall or late summer (don’t remember exactly). Actually one fry survived 2 weeks then died. Then, 2 weeks later a new fry appeared and it survived, and is now 10-12cm. Even the featherfin and Chinese are maybe up to 17-20cm.

    The 4 kois are around 2 years. We had one very big that was replaced by 5 kois, however, one died of unknown causes a year ago. I didn’t realize until yesterday that all our initial problems with too much mud over the fountain actually arose after the 5 kois started grow bigger.

    I honestly have a hard time to kill off the 2 old feathery goldfishes, however i have no idea what to do with them and the kois.

    Rüdiger advised me to get 20-30 Notropis spp, but i can’t seem to find them here in my area. I really have been slow to check it up, and i find the “regular” pet-stores that sell fish does not satisfy my curiosity, but i guess i have no choice but to ask the guy to come for the kois and give me some other fish. I know he has sick fish in his store at times, so yes i’m very skeptical.

    Current parameters are pH=7, GH=2, KH=3, NH3=0, NO2=Not 0, a slight color change in droplet test which i interpret as very low, NO3= ~20, but looks like increasing fast, Temp=23 deg. Celsius. No heater is installed as there is floor heating. Also there is a outlet in the pond for the tap water which is very cold.


    So, for my main question……what to act on first:

     – change to less and smaller fish?  I think thats me first priority.

     – Upgrade to more pump capacity?


    I would like to keep the catfishes (even though they are wasters too), and get rid of the koi/gold for other fish, or just go for a few goldfishes.

    The plecos are really becoming my favorite, but we do need some other nice fishes too.


    I never manage to keep it short, so really hope for all the reply and input as can get.









    Hi there Helene,

    it’s me again! :-D

    In my opinion, you are on the right trail of thought! As I did mention in my first reply, keeping large gold fish and koi in a “tank” like that is, apart from the mess, cruel.

    Upping pump capacity without increasing filter surface is counter productive, as flow rate will get too high to grant proper biological filtration. Imho, as long as you have to stick with your current stock, you’ll have to change 1/3 of the water (incl. vacuuming the substrate) at least every fortnight.

    Personally, I’d find a good place for the goldies and kois and get something a bit smaller and compatible with 25 cm water column! ;-)

    It’s difficult to give advice on fish species as I have no clue what you can get. Maybe there are some SF members out there in Norway who can help you out???



    edit: I’m not quite with you on changing the filter mat to 20 ppi!? You say you’ve got a “fine” filter foam in there now. Let’s assume it’s a 40 ppi. If you change that to 20 ppi you’d loose about half the surface which can be colonized by your filter bacteria, hence you’d loose roughly 50% biological filter efficiency. That is certainly not what you want?

Viewing 2 posts - 1 through 2 (of 2 total)

You must be logged in to reply to this topic.