Disinfecting before renovating tank?

Holy Samosa

Junior Poster
Dec 1, 2009
Hi guys.

This is a variation of a question I asked on another forum, but I really want to get solid advice from the Jedi Masters, so here I am. :)

I'm all set to completely renovate my planted tank which has been up and running for about 9 years, but almost completely neglected for the past 5. At different points in time this tank has been infected with every imaginable freshwater algae, but currently has a fairly extensive infection of BBA, diatoms, surface scum and some unknown brown slime.

It has a Flourite substrate rich with years of fish poo and super dependable Eheim filter which I plan to reuse, but other than that all plants and hardscape are being replaced. I have new lights, CO2 and fresh EI fertz ready to go.

So, my questions:

* Should I give the Flourite and filter a bleach bath to nuke any stowaway algae and spores? I know this would kill all of my beneficial bacteria as well and thus require the tank to cycle and also wash away the nutrient rich mulm. Is this a worthwhile tradeoff for starting algae free?

* Would disenfecting the substrate and filter with a strong Excel solution perhaps get the algae but spare the beneficial bacteria?

* Although I will be EI dosing, it seems worthwhile to supplement the Flourite before I replant, especially if I'll be loosing the mulm. What do you guys recommend? Someone on the other forum recommended a light dusting of peat moss, potash and chelated iron on the bottom of the tank. Thoughts?



Plant Guru Team
Lifetime Member
Sep 23, 2007
South Florida
Hi Jeremy,

IMO I would simply REPLACE the substrate. Take some sponges and soak in the existing tank for a few weeks to attract bacteria and use them in the 'new' tank. They will help a lot.

Use these after the substrate is replaced. Do a 50% water change every 2 days after the replacement for 2 weeks to help with any issues.

Your substrate makes a difference in plant growth and the aesthetics of the tank.

You have an opportunity to start fresh, I would take it..especially after 9 years, I think you got your money's worth lol

Is easier to do and you know you have a nice fresh substrate.

You can REALLY wash (not bleach IMO) the flourite and mix it with worm castings or such. There are lots of ways to improve/enrich an inert substrate. Some searching on this site will reveal many :) I would start with new flourite if you can afford it.


You can use ADA AS and the dry start method (DSM) to grow a nice carpet of plants for several weeks and than flood the tank. This helps alleviate the nh4 issue with new ADA.

The new black flourite is very nice and I used it in my 180 when I replaced the old flourite. One of the better things I did..

Plant heavy from the start with fast growing stems and the substrate will colonize quickly. Plants with roots will also have bacteria so use some from the old stuff.

Hope this helps.

Holy Samosa

Junior Poster
Dec 1, 2009
Hey Gerry!

Thanks for the advice. I'd love to go for the ADA AS, but I've already bought more Flourite to help add more slope in the next scape, plus I think the wife would throttle me when she saw the price tag of the AS. ;-) Maybe next time...

I do think I'll give the earthworm castings a shot, though.

So, should I bleach the filter?