By Bob Goemans
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Bob Goemans corresponds with Adam Thompson

Adam Thompson writes...

Hi Bob,

My questions are around the use of Chloroquine Phosphate (CP). I have read a lot of what you have put out there about the use of this product but have a couple of specific questions:

1. Lighting. You have noted that HO lighting can break down CP. Is T5HO going to be considered too much light? I have a 4 lamp unit of which I can have half off if necessary.

2. Refugiums. I currently run a refugium on my FOWLR tank. It used to be a reef tank. Since I currently rely in the macroalgae to help with filtration, is there a good way to convert it to something else? ADHI is the brand if it makes any difference. Or do I need to just trade it out for a wet/dry/Berlin type?

3. Has anyone noticed that right after the initial treatment of CP that the Crypto seems to briefly intensify? Not sure if this is due to the imbedded parasites dying and coming to the surface. I have noticed that when I have treated with CP at the first signs of a crypto infection that the fish have noticeably less white spots the day or so prior to the next treatment. However, within 24 hours of the first dose they are covered with white spots and then they slowly disappear. Not sure if this has to do with my dosage as I typically use 40mg/Gal which is half the 20mg/L that you recommend. Thank you!

Adam Thompson

Highlands Ranch, CO

Bob replies...

Hi Adam,

Thanks for your inquiry through, and must say there have been a lot of requests for similar data from a wide spectrum of hobbyists.

As to question 1, T5HO lamps are 'H'igh 'O'utput lamps, and since the medication is photo-sensitive, its effectiveness can be reduced. Yet - how to 'exactly' define the detrimental affect to the medication when certain types of light, i.e., its spectrum and intensity, impact a given amount of aquarium water no doubt containing various minerals/elements/compounds levels, is beyond my limits of expertise. All I can say with any assurance, if lighting is absolutely necessary, use low intensity level fluorescent lamps while treating.

As to question 2, even though there is much evidence that CP will destroy macroalgae, I have received a letter from an aquarist saying that CP usage had no negative affect on his 10 gallon refugium filled Chaetomorpha algae. Furthermore, the aquarist continued to light the refugium with low intensity compact lights opposite that of the main aquarium. The main aquarium was said to be treated at the 10 mg/l dosage, then a week later at the 20 mg/l dosage, with an additional 10 mg/l treatment one week later. I asked for some additional data, however, did not receive it, therefore, still unclear as to the survivability of Chaetomorpha in a CP treated system. You may want to test it yourself, and then update me so others will benefit in the future. And should note, the preferred first treatment is 20 mg/l, and the second through fourth treatment 7 days apart is 10 mg/l with about 10% water changes (* see below) prior to every additional dose.

As to question, 3, I have seen just the opposite in all previous letters! In fact, some aquarists were tempted to stop further treatments simply because their fish looked cured after one week of treatment. However, 'all' found that to be a fallacy and that the 'ich' parasite would return sooner or later. Now with that said, one must understand the cycle of the parasite being treated. In your case it's said to be Cryptocaryon. If so, and as stated in our book The Marine Fish Health and Feeding Handbook published by Microcosm, its life cycle can extend upwards of 28 days or more and undergo three stages: 1) the trophont stage, 2) the tomont stage, and 3) the tomite stage. The trophont stage is the period when the parasites are imbedded in the fish's skin, also known as the feeding stage. The tomont stage is when the parasites have fallen off the host and have encysted to reproduce, also known as the dividing stage. Finally, after many days, the cyst breaks open and tomites are released in swarms as the newly hatched parasites seek new hosts. Since the parasite is either under the skin of the fish or encysted during the two previous stages, it is 'only' during this final swarming stage that medications can actually kill the parasite. Therefore, timeframes of visible infection can vary somewhat depending upon the timeframe in relation to the first treatment and the overall conditions in the aquarium.

* And let me add something here, as there has been increased communications throughout 2011 as to some fishes seeming to lose their appetite while being treated with CP. To possibly overcome this situation, its recommended water changes prior to each follow-on dose be increased, e.g., 15 - 25% if this is occurring. Again, your follow-up to me is important, as I track all input so as to help all interested in CP treatments.

Hope this helps,



Ich; Fish Disease; Chloroquine Phosphate

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