Switching From Undergravel To Hob Filter.

I have a 20 gallon tall community tank that's been running efficiently on a highly effective undergravel filtration system for a year and a half. But as happy as I have been with my UGF performance I need the flexibility and water clarity an HOB provides. So I've decided I want to scrap my UGF and switch to a HOB.

So I went out yesterday and bought and installed an Aquaclear 50 HOB onto my tank. I added a prefilter to the intake tube and it's already doing it's job, improving water clarity by catching all the fine floating particles the UGF doesn't catch.

My question is now that the HOB is running and catching particulates from the water column, approximately long will it take before the HOB becomes seeded and I'm able to remove the UGF?
I understand the only way to get an instant cycle is by adding media from a cycled tank. But would running the new HOB alongside the UGF in an already cycled tank take as long as cycling from scratch?

 

So I just had a friend make this transition. This was on a 50 gallon system converting to a fluval canister filtration method. We added the canister and let everything run for 2 weeks. Then removed half of the plates, allowed 2 more weeks. Removed the other. If you only have one plate. I would allow the Hob about a month to really ensure it built up enough biomedia and then upon removal be ready for the tank to fluctuate a bit with its levels while the biocolonies replenish. This may mean more frequent water changes or the like...Just as long as you're on top of it it shouldn't be an issue.
If you're gung hoe on pulling the UGF you can do it quicker than we did it...we just didn't want to risk any issues. I'd say at minimum wait 2 weeks.

 

So I just had a friend make this transition. This was on a 50 gallon system converting to a fluval canister filtration method. We added the canister and let everything run for 2 weeks. Then removed half of the plates, allowed 2 more weeks. Removed the other. If you only have one plate. I would allow the Hob about a month to really ensure it built up enough biomedia and then upon removal be ready for the tank to fluctuate a bit with its levels while the biocolonies replenish. This may mean more frequent water changes or the like...Just as long as you're on top of it it shouldn't be an issue.
If you're gung hoe on pulling the UGF you can do it quicker than we did it...we just didn't want to risk any issues. I'd say at minimum wait 2 weeks.

Great advice, thanks!!
I remember this 20 gallon UGF (unlike my 10 gallon UGF that uses 2 plates) consisted of about 10 plates that joined/slotted together. So it should be a snap to remove small sections of it over the course of a few weeks.
I'm not in a big rush or anything, but I'd like to get it done sooner than later without completely crashing my cycle.

 

I agree with the above and would definitely let it run for a good month or even longer if your in no major rush to remove the UGF. Great choice on the new filter for your 20. I run an AC50 as well as a Fluval 206 and a dual sponge filter on my heavily planted 20 long but I may be slightly overstocked seeing its loaded with guppies ( many generations ) 2 otto cats a clown pleco 2 nerites and some ramshorns and 2 True SAE

 

Great advice, thanks!!
I remember this 20 gallon UGF (unlike my 10 gallon UGF that uses 2 plates) consisted of about 10 plates that joined/slotted together. So it should be a snap to remove small sections of it over the course of a few weeks.
I'm not in a big rush or anything, but I'd like to get it done sooner than later without completely crashing my cycle.

Oh perfect! Yea just remove like 2 sections a week and you should be golden.

 

Op, I'm facing a similar problem. I added a sponge filter and new HOB, to replace my existing bio-wheel HOB. My old HOB only had polyfill instead of cartridges so I moved my polyfill from the old hob to the new one and added two fresh cartridges to the old hob. I'm going to give it a month then rip the pad from one of the cartridges and put it into the new HOB. In 2 more weeks, I'll take the pad from the 2nd cartridge and add it to the new HOB. Two weeks after that, I'll pull the old HOB, and watch my water parameters to make sure everything is cool.

Maybe you can use a similar approach with the UFG. Monitor your water for a mini-cycle, and all should be ok.

 

I agree with the above and would definitely let it run for a good month or even longer if your in no major rush to remove the UGF. Great choice on the new filter for your 20. I run an AC50 as well as a Fluval 206 and a dual sponge filter on my heavily planted 20 long but I may be slightly overstocked seeing its loaded with guppies ( many generations ) 2 otto cats a clown pleco 2 nerites and some ramshorns and 2 True SAE

Sounds like my same situation I have with 2 of my other tanks lol:

My 37 gallon has an AC70, Marineland C220 canister and 40 gallon sponge.

My 38 gallon has an AC70, Marineland C160 canister and 40 gallon sponge.

Talk about over filtering lol.
I realize I could easily swap filters or media to jumpstart the AC50 in my 20 gallon but my 37 and 38 contains my pride and joy and are heavily stocked so I really don't want to mess with them.

I was originally going to go with the AC30 on my 20 gallon but thank goodness Petsmart price matched the deal on chewy so I got the AC50 for the same price I would have paid for the AC30, winner winner chicken dinner

 

I would run the new filter for a month or 2 if you can leave it in without any hassles. The biggest problem your going to have is the amount of gunk that's built up under it over the last yr and a half.

I would personally try and get a hose or something under it while you do you weekly water changes to remove as much as you can before you replace it.

Also depending on your tank, I wouldnt do it if its planted, you can run a reverse flow ugf with a power head to increase your filtration, just make sure you use a pre filter on the power head.