Bottled bacteria products for Koi ponds – something that cause discussion and debate amongst Koi keepers second only to the use of salt on ponds, itself a topic for another day….

For every product that has a die hard fan, you can be sure to find someone who will rubbish the same product as ‘useless’.

Even if a particular product seems to have been effective in ‘starting’ or ‘boosting’ a filter, you can never be sure what would have happened without the product being added either.

And finally, without the use of accurate test kits, measuring the real effectiveness, or otherwise, of a product is difficult.

In this post I will recount my personal experience of the Colombo Bactuur Filterstart and Activator products marketed under the Dutch Colombo brand, part of the Aquadistri Group, which also includes the Ornafish and Superfish brands.

Colombo Bactuur Filterstart and Activator

Colombo Bactuur Filterstart and Activator

The story originally dates back to the spawning which took place on 15th July and the subsequent fry which hatched.  The plan for these fry was to grow them in the indoor tank without a net, as such the gravity fed Nexus wasn’t an option for filtration, however the plan was to put a temporary shower/trickle filter on the tank, fed by a submersible pump.


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For the first few weeks everything was great, the fry were growing rapidly, and I had no reason to even consider there were any problems.  A water test in mid August suddenly showed elevated ammonia levels, thereafter off the scale nitrite readings followed, fry couldn’t be fed properly and the long and short of it was we lost control of the water completely, by the time things were back under control the damage to the fry was sadly done.

Having taken the losses on the chin, the tank was cleaned down in preparation of a hoped 4th round of spawning, somewhat late in the season.  At the same time we had purchased one of Gatwick Koi Shower/Protein Skimmer units to try, particularly being interested in the skimmer side of its ability to remove ‘toxins’ that perhaps inhibited fry growth.

Gatwick Koi GK Pro Skim Mini

Gatwick Koi GK Pro Skim Mini

The top 2 tiers of the unit were filled with Alfagrog which had been used in the temporary shower so it had some ‘life’ to it.  It was switched on on 9th September.

On 12th September the parents were put together in the tank which had been filled with fresh dechlorinated tap water.

Parents set for spawning 12th September

Parents set for spawning 12th September

Spawning completed in the early hours of the morning on 13th September, I wasn’t surprised to see a slight ammonia level of 0.08 reading on the Hanna Pocket Checker.  The following morning this has been largely mopped up by the filter.

Post spawning ammonia levels

Post spawning ammonia levels

It was however a nitrite reading taken on the morning of 14th September that surprised me and put me on alert.  I certainly hadn’t expected a reading of 164ppb (0.164mg/l).


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Nitrite reading, 14th September, 11:15

Nitrite reading, 14th September, 11:15

The following morning the level had risen to 235ppb, an upward trend which continued over the next 24hours.

Escalating nitrite levels 15th and 16th September

Escalating nitrite levels 15th and 16th September

Clearly something needed to be done to halt the trend, at this point the fry were just on the verge of hatching, large scale water changes really weren’t an option.

Last year I wrote about using a product called ‘Nitreat’ – http://nishikigoi.life/2019/05/07/pond-update-and-spawning-plans-where-does-time-go/ – a product I will never really know whether it was entirely successful in treating nitrite.  I was however prepared to bite the bullet and order some again.  On checking the manufacturers website it seems they are no longer making the product, one that’s significantly more expensive than other filter start products.

I took a trip to Manor Koi to get some ‘bacteria’.  Colombo manufacture my go to liquid dechlorinator, and on the shelf next to it I spotted the Bactuur Filterstart.  The 1 litre bottle would deliver 5x200ml doses in the tank so I decided nothing ventured nothing gained.

Bactuur Filterstart instructions

Bactuur Filterstart instructions

I noted that it recommended using with the ‘Activator’ product which was on the shelf next to it so figured in for a penny, in for a pound, get both.

Bactuur Activator instructions

Bactuur Activator instructions

I would guess it around 4pm on 16th September that the first dose of 200ml of Filterstart and 200ml of Activator was added.  Rather than just adding to the pond I rather awkwardly administered directly to the middle tier of the shower which involved a length of 40mm pipe resting on the lip of the tier through which the mix was poured.


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Later that evening I decided to take another nitrite reading, more in optimism, and out of despair that it would have deteriorated further, than anything else.  To my surprise the reading was exactly the same as just over 7 hours previous.  In the 7 hours before that, as shown in the images above, the level had increased by 42ppb, and the 12 hours prior to that by 100ppb.  So a glimmer of hope was that we had stopped the rising trend.

Nitrite reading 16th September 22:10

Nitrite reading 16th September 22:10

Interestingly the ammonia reading at the same time was pegged at zero which is pretty much where it has been ever since, occasionally reading 0.01 or 0.02, which is well within the accuracy levels for being zero on the Hanna Pocket Checker.

Ammonia reading 16th September 22:11

Ammonia reading 16th September 22:11

Over the course of the following 4 days nitrite levels showed a continual downward trend when tested a twice daily intervals.

Nitrite readings 17th-20th September

Nitrite readings 17th-20th September

One thing I must state is that I ended up slightly overdosing the product, a double dose was given in the first 24 hours and then every 24 hours thereafter, although i’m not sure that had any significant bearing.

What I can say though is that 1 week ago I had concerns about nitrite levels in the pond where the fry were about to hatch, now the concern is gone.

As I said a the beginning of the post, we’ll never know whether the nitrite level was due to drop naturally anyway.


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Given such a situation occurring in the future I will certainly be happy to turn to Colombo Bactuur Filterstart and Activator.

Want to know more about the Hanna Pocket Checker units?  See my hand on review of these excellent pieces of kit here – http://nishikigoi.life/2020/06/07/hanna-pocket-checkers-a-hands-on-review/


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