20 Gallon Goldfish Tank Always Keeps Getting High Ammonia.

  1. wapooshe Member Member

    I have a bare bottom 20 gal goldfish tank and have 2 fantail goldfish (2.5 inches) I know that this tank is not large enough for them when they are adults but as of now I believe it's a good size for them to be in at the moment. I feed them only once daily and not alot, my water has ammonia reading of 0 and I do weekly 50% water changes. The problem is that every time after a water change ammonia is 0 and then it rapidly rises to like 1.5-2.5 ammonia. I know goldfish do produce a lot of waste but I don't think they should be producing so much as to cause such a rapid rise. Also my tank is bare bottom and I barely see any waste...
  2. BottomDweller Fishlore VIP Member

    They produce a huge amount of waste. What is the GPH of your filter? 50% once a week is not enough IMO. I currently have a 3" goldfish in a 21 gallon quarantine and am doing 60-70% water changes three times a week.
  3. Over It Well Known Member Member

    Have you tested your tap water for Ammonia?

    They are huge waste producers and have a huge bio-load. Most likely your filter is not able to keep up and you need to do more frequent water changes.

    I have 2- 2in. Fantails in a 36 gal with 2 Marineland Pengiun Bio-Wheel 200 filters and I still do 25% twice a week or more. I will be upping that very soon I'm sure.
  4. Books&Fish Well Known Member Member

    For now, without upgrading their tank, you need to upgrade your filter. Either add more media capable of growing more ammonia- and nitrite-eating bacteria or just buy a larger filter that has the capacity to hold more media (and transfer over your old media so you don't lose your cycle).

    For reference, I kept 2 fantails in a 40 breeder with an Aquaclear 110 (500 gph) with extra media and a corner filter full of media also. Never had water quality problems, but have since moved them to my parents' 1.3 acre pond.
  5. Over It Well Known Member Member

    I agree with this, but I would even suggest running both filters on the tank at the same time. Always better to have 2 filters than one.
  6. wapooshe Member Member

    Thanks for the replies. I do not know my gph of my filter but I believe it is sufficient as I can not see any waste in my tank (since it is a bare tank). Adding another filter wouldn't be a problem I just don't know if its necessary if it picks up all the waste in the first place.

    do you think bacteria could be a problem? I mean my tank is bare so it has little room to grow bacteria other than the tank itself and the filter. Do you think that my tank lacks bacteria and is the source of the increase in ammonia or something else?
  7. Books&Fish Well Known Member Member

    Most waste is not visible so that has no bearing on how "dirty" a tank is or how toxic. Your gph is likely NOT sufficient, which is why you have water quality issues. Bigger filter or second filter of the same size might be okay too.
  8. wapooshe Member Member

    ammonia is 0
  9. Books&Fish Well Known Member Member

    90% of your waste-eating bacteria grows in the media in your filter. Very little grows in the substrate or plants, etc.

    If your tap ammonia is 0, that just strengthens my statements. More media or another filter (or bigger filter) :) So yes, your filter lacks bacteria and is the source of the increase in ammonia.
  10. wapooshe Member Member

    Well it's hard to make an estimate on my gph right now. All I can remember is that the box said made for 20 gallon or 30 gallon tank. It's a HOB and has filter pads. It is made by nat geo and I can't find it online. What do you think my gph is and how much do I need to add so I can have enough.
  11. Books&Fish Well Known Member Member

    What brand and model? A google search will tell you how many gph. Manufacturers don't suggest a high enough gph for the tank size. So a filter the mfg claims is good for 20-30 gallon tank probably has 120 gph or so, which if you did the math of 20 gallons x 8-10 times turnover per hour is 160-200 gph. Which as you can see, is not enough. I don't know why they estimate low since more gph filters cost more.
  12. Over It Well Known Member Member

    I would suggest getting a filter that's made for a tank that is at least 40 gallons and using that along with your other filter. I personally really like the Marineland Bio-Wheel filters. They have room for a lot of filter media and they have the Bio-wheel which also houses your beneficial bacteria. I'd go for the 200 like mine if it were me. I've also heard lots of good stuff about Aqua Clear filters.
  13. Books&Fish Well Known Member Member

    upload_2017-7-11_15-6-52.jpeg upload_2017-7-11_15-7-0.jpeg upload_2017-7-11_15-7-5.jpeg One of these?
  14. Books&Fish Well Known Member Member

  15. Books&Fish Well Known Member Member

  16. wapooshe Member Member

    wow I cant believe you found it! my filter would be the PF30 then
  17. Books&Fish Well Known Member Member

    Google knows all things. ;) With the PF30, you're still short 10 gph with regular stocking, but a pair of goldfish are heavy waste producers, so you need much more. Like I said, I have a 40 gallon with an Aquaclear 110 at 500 gph. That kept up just fine with a pair of fantails and weekly water changes. Double the waste dilution and almost 4 times the turnover than you have now.
  18. AllieSten Fishlore VIP Member

    For a normal bioload the recommendation is 8-10 x's tank volume for gallons per hour. So for a 20 gallon tank, you need a filter with 200 gallons per hour. For a normal bioload. For goldfish you need more than that. I would shoot for 300gph.

    I have a 30 gallon tank with a filter that has 450gph with 2 sponge filters. You cant have too much filtration. You can however have too little. The size of your filter is directly related to your Ammonia level. Along with have large bioload producing fish.